Abstract:In order to overcome the difficulty in maintaining the instability of drilling fluids after high calcium contamination ，ahigh temperature resistant and high calcium tolerant fluid loss agent DF-1 was synthesized using2-acrylamide-2-methyl propane sulfonic acid （AMPS）， acrylamide（AM）and diallyl dimethyl ammonium chloride （DMDAAC）monomers. The optimum synthesis condition was obtained as follows: 4.1∶2.9∶3.0 the monomer mass ratio of AMPS ∶DMDAAC∶AM，0.3% initiator ammonium persulfate ，7 pH value ，40℃reaction temperature and 3 hrs reaction time. Laboratory evolution experiment results showed that under 40000 mg/L CaCl₂ contamination and hot rolling16hrs at 150℃，basic mud with adding DF-1 could maintain the apparent viscosity in 9 mPa·s and the API fluid loss in 16mL；and that of basic mud without aging was 7.5 mPa·s and 30mL，respectively. The mechanism of DF- 1 was revealed by IR、TGA、SEM and EDS analyses. The IR analysis result showed that the polymer contained —CONH₂ and quaternary ammonium group ，which could help it to strongly absorb on bentonite by hydrogen and ionic bonds. TGA analysis result showed that DF- 1 had excellent thermal stability within300℃. EDS and SEM analysis results indicated that the relative calcium ratio of mud API cake in calcium contamination could reduce from 15.96% to 3.77% after adding DF-1，which attested that DF-1 was able to effectively decrease the ion exchange absorption of calcium on bentonite，thereby could prevent the bentonite particles from being coagulation and form a dense cake.

Abstract:An amphoteric polymer anti-sloughing agent named WPZY-1 used in air-mist/foam drilling was synthesized using cationic monomer (YD-1), acrylic acid, acrylamide and alkyl substituted acrylamide as raw material, and ammonium persulfate and sodium bisulfate in mass ratio 1:1 as initiator. Its inhibition and anti-sloughing performance was investigated. The optimum dosage of initiator, AA and YD-1 was 0.5%~1.0%, 3%~5% and 5%~10% of total monomers. The performance evaluation results showed that WPZY-1 had strong adsorption capacity and good anti-sloughing property, with a saturated adsorption amount of 100.98 mg/g. The secondary shale recovery rate in 0.5% WPZY-1 solution after 48 hrs was 99.3%. The expansion amount of core after 24 hrs was 1.58 mm. Moreover, the artificial core soaking in WPZY-1 solution could keep regular integrity shape after 10 d with no cracks and peeling phenomenon. WPZY-1 had good compatibility with air-mist/foam drilling agents and its application could effectively improve the inhibition and anti-sloughing performance, and extend wellbore stability time, which met the requirements in high water exit formation.

Abstract:Few studies had been done about the nature and strength of gel slug which was used to seal oil and gas in wellbore. Based on the theoretical calculation, we analyzed the stress-strain properties of gel in wellbore, and combined with gel tensile, compressive and shear experiment analysis, determined that the gel slug played the role of sealing mainly depending on the gel shear resistance which could be described by the parameter of shear strength. The calculation results showed that the strength of gel slug sealing in wellbore was directly proportional to the length and shear strength, and was inversely proportional to the wellbore diameter. The measured data had verified the theory. At the same time, a new test method of shear strength about gel was established, and the corresponding test equipment was developed. Research result provided a theoretical guidance to formula research with high gel strength and technical process design.

Abstract:Combing acid fracturing with proppant can achieve the high fracture conductivity of fracturing with sand and multi-fracture system of conventional acid fracturing. Performance of acid system has significant influence on treatment effectiveness. In view of the present situation of lack in crosslinked acid system suited to be applied in deep and high temperature formations, a novel high temperature resistant and proppant transportable crosslinked acid system was developed based on laboratory research. The formulation was as follows, 20% hydrochloric acid +1.0% thickener YT-217+1.6% crosslinking agent JQ-1+0.4% crosslinking agent JP-2+2% high temperature corrosion inhibitor JG-1 + 1% cleanup additive JZ-1 +1.5% ferric ion stabilizer JF-1.The experimental results showed that crosslinking time of the system was 95 s, indicated that the system possessed the crosslinking-delay properties. The fluid system had a good temperature and salt resistance performance, the viscosity of the system could maintain up to 50 mPa?s after sheared at the temperature of 150℃and the shear rate of 170 s-1 for 120 min. Furthermore, the system exhibited the peculiarity of completed gel breaking, good compatibility with formation and strong proppant-carrying capacity, which ensured that the fluid system could meet the requirements of the fracturing treatment.

Abstract:In this paper, hexamethylenetetramine, concentrated hydrochloric acid was used as raw materials to prepare a small molecule clay stabilizer—hexamethylenetetramine hydrochloride and its anti-swelling rates and mudstone loss rate were investigated. The results indicated that the synthetic method was simple and the reaction was insensitive to reactant ratio and temperature. The optimal hexamethylenetetramine hydrochloride was obtained when the ratio of hexamethylenetetramine and concentrated hydrochloric acid was of 1:1.5, at the room temperature and at the reaction time of 0.5 h. When the mass concentration of the optimal hexamethylenetetramine hydrochloride was of 0.5%, the anti-swelling rate and the mudstone loss rate reached 78% and 10%, respectively. When hexamethylenetetramine hydrochloride was combined with PDADMAC with mass ratio of 3:2, the effect of anti-swelling clay was further improved.

Abstract:In this paper, the crosslinking process of kerosene-based and diesel-based fracturing fluids was studied with dialkyl phosphate ester as gelling agent and complex iron as crosslinking agent, and the rheological dynamics models, which were respectively suitable to describe the crosslinking process of kerosene-based and diesel-based fracturing fluids, were established. The results showed that the second-order and third-order rheological dynamics equations could be applied to describe the crosslinking process of kerosene-based and diesel-based fracturing fluids, respectively, the calculated values were in good agreement with the experimental data, and the meanings of the model parameters were reasonable. With the increase of the concentration of the gelling agent, the structure change rate constant (k) decreased and the maximal elastic modulus (G′max) increased.

Abstract:The relationship between macroscopic properties of fracturing fluid, molecular microstructure and fracturing fluid proppant carrying capacity was studied through static state proppant settlement experiment, dynamic viscoelastic test, yield stress test, scanning electronic microscope observation. Proppant settlement experiments showed that?a?nonlinear?relationship?existed?between the change of viscosity of fracturing fluid and proppant settling rate, which indicated that viscosity index could not characterize the carrying capacity of fracturing fluid accurately. Dynamic viscoelastic tests showed that the increase of loss modulus was favorable of reducing the rate of proppant settling, while a significant increase of storage modulus which endowed the fluid elasticity maybe the main reason for proppant keeping suspension for a long time in crosslinked fracturing fluid. Fracturing fluid microstructure analysis showed that the fracturing base fluid possessed a disorder, loose, plurilocellate, and mesh-stacked structure, while the crosslinked fracturing fluid possessed a well-distributed, close and the whole-stacked structure, endowing the elasticity of crosslinked fracturing fluid and causing a essence change of fracturing fluid proppant carrying capacity.

Abstract:The conventional metal crosslinked fracturing fluid system have some weakness, such as great toxicity and the produced second pollution to the formation duiring crosslinking process at alkaline condition;while the non-metal ion crosslinked fractureing fluid system also has some problems, such as slow gelling rate and poor shear resistance performance. In the paper, a low toxicity fracturing fluid with a novel cross-link agent system was prepared, the best formula of the fracturing fluid were obtained by analyzing the main factors affecting gel performance, the high temperature and shearing resistance and demulsification performance were investigated. The experimental results showed that, when the thickener content was 0.15%, the amino sulfonic acid content was 0.15%, the ethanol content was 1%, the of coagulator content was 0.020%—0.025%, the crosslinking agent content was 0.25% and the potassium chloride content was 0—2%, the fracturing fluid with the excellent performance could be prepared. the gelling time of the optimal fracturing fluid was about 150 s, and the initial viscosity after gelling was of 1529.0 mPa·s. When the fracturing fluid was continuously sheared at the temperature of 100℃ and the shearing rate of 170 s^-1 for 60 minutes, 90 minutes and 120 minutes, respectively, the viscosity was of 259.9 mPa ?s, 197.4 mPa ? s and 166.8 mPa ?s, respectively，indicating that the fracturing fluid had strong high temperature and shearing resistance. The gel can be broken totally with 0.03% of potassium persulfate at the temperature of 90℃within 3 hours. The gel-broken fluid was clear, and the viscosity was only 1.07 mPa·s. The fracturing fluid system did not contain any toxic metal ions, reducing the damage to formation.

Abstract:In this paper, non-aqueous liquid guar concentrated suspensions (NALGCS) were prepared by mixing hydroxypropyl guar gum, polyethylene glycol and suspending agent. Apparent viscosities, suspension ratio and hydration rates of the NALGCS were evaluated and influencing factors of quick hydration of the NALGCS were further discussed. Results of rheological experiments and settlement observations showed that quaternary ammonium salt modified montmorillonite was suitable as a suspending agent of the NALGCS. With the increase of the suspending agent content, apparent viscosities of the NALGCS slightly increased, and suspension ratio sharply increased. The apparent viscosity of the NALGCS with 5% of the suspending agent was about 650 mPa·s at shear rate of 340 s-1, the suspension ratio was approximate 100% within 1 d and above 98% within 2 d. Apparent viscosities of the NALGCS with powder liquid ratio (mass ratio of guar gum to polyethylene glycol) of 1:5—1:2 was 200—700 mPa·s at shear rate of 340 s-1, indicating that the NALGCS possessed good flowability, moreover, it was beneficial to pump guar concentrated suspensions into continuous mixing vehicles. Results of hydration experiments showed that a quicker hydration rate of fracturing base fluid prepared using the NALGCS was found under the condition of weak acid, comparing with under the condition of neutral environment, however, the NALGCS could not hydrate under alkaline condition. The pH value of the dosed water was 5, the 85%-90% of maximum viscosity of the base fluids was achieved within 3—5min. Higher shear rate would also accelerate hydration of guar concentrated suspension.

Abstract:The gel system composed of polyacrylamides and zirconium acetate was investigated in the paper. The change of the viscosity of the gel system was investigated in the crosslinking reaction process. The reaction process could be divided into three successive steps: induction period, rapid cross-linking period, and stabilization period. The gel formed in a 3-dimensional network structure was confirmed by environmental scanning electron microscopy (ESEM). With the increase of polymer concentration and crosslinker concentration, reaction temperature and salt content, the gelation time reduced, and the gel strength increased. Three salts were arranged according to their influence on gelation system in following order: CaCl₂ > MgCl₂ > NaCl. A solution with pH value of 7-8 was the best suitable for the gel system. the gel system was suitable for the reservoir with the temperature below130℃.

Abstract:Considering an offshore oilfield was a sandstone reservoir and its completion had characteristic of gravel pack, this paper studied the acidification plug pre-removal system. After the determination of type and concentration of acid, screening of additives and physical simulation experiment, acidification plug pre-removal system was determined. Ahead acid and overflush acid were preliminarily confirmed as hydrochloric acid with mass fraction of 7%. The formula of primary acid was preliminarily established: 5% hydrochloric acid, 5% fluoboric acid, 1% acetic acid. The corrosion rate to stabilized na-bentonite of ahead acid and overflush acid was only 2.78% and that of the primary acid was up to 21.77%, while the corrosion rate to gravel of that was 0.38% and 1.04%, respectively. The optimum dosage of corrosion inhibitor BJ was 0.5% and the rate of corrosion inhibition was more than 95%. While the optimum dosage of clay stabilizer WS-1 was 3% and the rate of anti-swelling was 85.96%. The best formula of acidification plug pre-removal system was obtained as follows: ahead acid and overflush acid consisting of 7% hydrochloric acid, 0.5% BJ and 3% WS-1, main acid consisting of 5% fluoboric acid, 5% hydrochloric acid, 1% acetic acid, 0.5% BJ and 3% WS-1. The system had good compatibility. The effect of plug removal was satisfying while the permeability recovery ratio was improved more than 7 times. The acid fluid system could dissolve the flocculation, produce larger pores, and improve the permeability to achieve the purpose of plug removal.

Abstract:Most of the sandstone reservoirs contained a little clay, and water flooding technology would induce clay fines migration. The important factors causing clay fines migration included clay surface charge, double electric layers, clay mineralogy, exchangeable cation, water salinity, water film and so on. According to relative literature investigation, clay fines could start to dislodge from pore surface only when the retention concentration of pore surface clay fine was greater than critical retention concentration. Then Bedrikovetsky’s critical retention concentration function was deduced by this theory. Although clay swelling and fines migration all result in formation damage, fines migration was able to improve reservoir porosity and permeability heterogeneities, alternate wettability, plug high permeability path, enhance washing oil coefficient and reduce water-cut according to the theory of clay fines migration analysis. Therefore, fines migration under proper control was good for enhanced oil recovery.

Abstract:The adsorption capacity of anionic and cationic polymer was a mainly indicator for investigation of water shut-off capacity, so the static and dynamic adsorption capacity were investigated. The experiment results showed that the adsorption equilibrium mass concentration of anionic and cationic polymer was 1000 and 1500 mg/L, and the adsorption equilibrium time of that was about 6 and 8 hrs. Temperature had a slight influence on the adsorption of anionic and cationic polymer. However, the adsorption increased with increasing hydrophilicity of core, and the adsorption capacity on hydrophilic core was much larger than that on lipophilic core. The dynamic adsorption quantity of anionic polymer with single injection, anionic polymer and cationic polymer with alternative injection, cationic polymer with single injection, and cationic polymer and anionic polymer with alternative injection was 61.77, 103.99, 119.64 and 137.61 mg/g, respectively. The alternative injection polymer could form a multilayer on the core which could effectively plug the big channels. The visual simulation result showed that the oil recovery of water flooding reached 60% after alternative injection of cationic and anionic polymers. Field application in Shuangqian 6 well of Henan oilfield showed that the profile was effectively improved, the water cut obviously decreased and the oil increased after alternative injection of three round polymers in 2010.

Abstract:In order to probe the effect of CO₂ on super heavy oil in CO₂ assisted steam huff and puff technology, physical properties of super heavy oil in Zheng 411 reservior under different amount of CO_{2 injection, different pressures and different tempretures were studied through gas injection swelling tests systematically, and predictive models for solution gas-oil ratio, bubble point pressure, oil viscosity, oil density and volume factor with CO2 content, pressure and temperature were established by means of multiple regression with high accuracy. The results showed that the solution gas oil ratio of the studied super heavy oil increased with the increase of the CO2 content linearly; the bubble point pressure increased with the increase of the CO2 content linearly, and increased with the increase of the temperature in a strong power relation; the oil viscosity decreased with the increase of the CO2 content exponentially, the natural logarithm of which decreased with the increase of temperature exponentially; the oil density decreased with the increase of the CO2 content exponentially, and decreased with the increase of temperature logarithmically, while increased with the increase of pressure linearly; the volume factor increased with the increase of the CO2 content exponentially, and increased with the increase of temperature exponentially, while decreased with the increase of pressure linearly. The viscosity of super heavy oil is very sensitive to temperature, and the oil mobility will be improved with the increase of temperature. Besides, dissolved CO2 can reduce the oil viscosity and swell the oil, which is helpful for the production of super heavy oil.}

Abstract:The changes of pressure and saturation, the production characteristics and distribution of remaining oil about low tension foam system under simulated reservoir condition of Shengli oilfield were studied by sand-pack and consolidated physical models. The results showed that the low tension foam flooding could increase the injection pressure of whole model, and improve the formation heterogeneity through profile control and fluid division. It was found that as the gas floating effect could be ignored in the early stage of foam injection, due to the viscous and capillary force, the low tension foam was mainly in the middle and lower parts of the model and the pressure in middle and lower parts was relatively a little higher. But at the later stage, foam distributed evenly in the model and could be displaced like a piston under the comprehensive effect of gas floating and viscous forces. As a result, the pressure changed more gently. Remaining oil mainly gathered in the outlet of the model, and the displacement efficiency near the inlet of the model was the best. Under the charge of the displacement of low tension foam, and in combination with gas buoyancy and oil washing effects, oil was mainly recovered at the initial stage of subsequent water flooding, and finally the integrated oil recovery was increased by 28.92%. Furthermore, the displacement efficiency in high and low permeability layers was much better.

Abstract:The optimum foam system was composed of 0.5% foaming agent ZY (petroleum sulfonate) and air in gas liquid volume ratio1.2:1. The foam’s volume was 400 mL, foam half-life was 540 s and apparent viscosity of foam was 1210 mPa·s. The mathematical expression of effective viscosity μ_X of air foam penetrating in pour medium at different sites on compacted sand stones spacing normalized from injection was deduced based on the Darcy and quantity balance laws. And the shear rate of γ foam penetrating was deduced according to the core pore throat diameter and the foam seepage velocity. Moreover, it was calculated that the relationship between μ_X and γ when the foam system was flooding in porous media. And the mathematical expression was μ_X=Kγ^n-1 . The consistency factor was 375.94 and the power law index was 0.33.

Abstract:Under the reservoir conditions of Wen 120 block in Huabei oilfield with 87℃ and 28291 mg/L salinity, the effect of permeability ratio on oil displacement efficiency of air foam flooding was researched with four groups of physical models which were made of different mesh number of quartz sand, whose permeability ratio was 2.8, 6.8, 8.9 and 10.7 respectively. The results showed that the enhanced oil recovery rate of high permeable tube, low permeable tube and double tube increased first and then decreased with increasing permeability ratio. When the permeability ratio increased from 2.8 to 8.9, the enhanced oil recovery rate of high permeable tube increased from 15.13% to 18.56%, that of low permeable tube increased from 19.45% to 29.81%, and that of double tube increased from 17.24% to 23.43%. The foam system enhanced the ability of profile control and water plugging in high and low permeability layer, and the effect of oil displacement became better. When the permeability ratio reached 10.7, the enhanced oil recovery rate of high permeable tube, low permeable tube and double tube was 13.55%, 9.00% and 11.74% respectively. The ability of profile control and water plugging of foam system reduced in high and low permeability layer, and the effect of oil displacement became worse.

Abstract:The improving oil recovery experiment of fracture dense high salinity reservoir was carried by air foam flooding. The ability of foam foaming agent，the half-life and salt resistance，and the effects of gas-liquid ratio on foam stability were evaluated by use of self-developed high-temperature and high-pressure device. The matrix core injectivity of air foam flooding，oil displacement efficiency and the ability of improving seepage cracks were researched through physical simulation device. The results showed that the foam volume of SFR-173 anionic-nonionic foaming agent in deionized water and simulated formation water was 290 and 340 mL，the half-life of that was 368 and 330 min，and the foam composite index was 6370 and 6697，respectively，indicating best foam performance. When the salinity increased from 7 to 56 g/L，the foam volume of 0.5% SFR-173 decreased from 370 to 340 mL，producing liquid time decreased from 174 to 122 s and the half-life reduced from 778 to 330 min. Under the formation condition，the foam volume increased and became gradually stable with increasing gas-liquid ratio. The optimum gas-liquid ratio was between 1∶1 and 2∶1. Air foam injection results in dense oil reservoir showed that with the increase of injection volume，the core pressure at both ends and the drag coefficient increased and became gradually stable，and the maximum value was 31.4 MPa and 1.74，respectively. The oil displacement efficiency increased by 17.86% after water flooding transferred to air foam flooding. Under the condition of crack heterogeneous reservoir，the water flood oil recovery was only 39.14% when the moisture content was 98%. The air foam flooding could effectively improve the utilization of core matrix condition and seal cracks seepage channel. The oil recovery of matrix core increased from 12.59% and 21.21% to 49.87% and 72.0%.

Abstract:Aimed at the problems of high filtrational resistance and low injection capacity in the development of high viscosity oil reservoirs with low permeability, the complex viscosity reducing system, composed of chemical heat generating agent and catalytic cracking agent, was proposed to reduce oil viscosity and improve oil recovery of the type oil reservoir. Laboratory experiment was conducted in high-temperature and high-pressure (HTHP) reaction kettle to optimize reaction conditions and catalytic agent type, and then the core flooding experiment was conducted to evaluate the effects of injection mode on the oil recovery and the injection capacity. The results showed that when the 200 mL of the NaNO2 solution with molar concentration of 4 mol/L reacted with 200 mL of the NH4Cl solution with molar concentration of 4 mol/L at the pH value of 2 in the reaction kettle with 400 mL volume, the temperature in the reaction kettle increased from 55℃ to 204℃, pressure increased from 10 MPa to 13.4 MPa after reacting for 6 min. The catalytic system, composited of oleic acid nickel (main catalytic agent), 7% formic acid (hydrogen donor), 7% urea (adjuvant) and 0.13% sodium dodecyl benzene sulfonate( emulsifier), could decrease the viscosity of the stock tank oil from Niujuanhu oil field by 65.3%. The oil recovery of water flooding, NaNO2 and NH4Cl alternating flooding, NH4Cl and NaNO2 alternating flooding, chemical heat generating and soaking interval flooding, and chemical heat generating and catalytic cracking and soaking interval flooding were 30.6%, 38.8%, 40.8%, 43.7% and 49.0%, respectively. Therefore, chemical heat generating and catalytic cracking and soaking interval flooding was the best injection mode, which could enhence oil recovery by 18.4% based on the water flooding.

Abstract:For the problem that the excessive fuel reservoir bring on the huge requirement of air injection when it is burning, and the economic evaluation result of fire flooding is not ideal, an indoor physical simulation experiment of in-situ combustion was conducted by adding two metal catalytic, ferric nitrate and zinc nitrate. The experiment results showed that, the gas composition fluctuation of the ferric nitrate catalytic experiment during the process of heavy oil fire flooding was greatly reduced compared to that of the blank experiment and zinc nitrate catalytic experiment, ,and the oil-producing time of ferric nitrate catalytic experiment was earlier than that of the blank experiment and zinc nitrate catalytic experiment; the ferric nitrate catalyst could increase the oxygen utilization ratio from 90.5% to 96.7%;?the content of the heavy oil burnt increased form 43.92 kg/m³ to 52.73 kg/m³, increasing by 20%; the air-fuel ratio decreased by 19.5%; at the same time,? the propulsion speed of fire flooding combustion front accelerated, and hydro/carbon ratio, heat of combustion, and deposition quantity of fuel also changed significantly.

Abstract:Hydrophobic associating polymer plays an important role in polymer flooding，profile control and water plugging for its fine salt resistance and shear resistance，however，there is the problem of adaptation with reservoir heterogeneity at the same time.In the paper，using reservoir characteristics and fluid properties of Bohai as studying platform，the compatibility between hydrophobic associating polymer AP-P4 and reservoir pore throat was confirmed，and then the adaptation between AP-P4 and reservoir heterogeneity was studied through analyzing the influence of polymer concentration changes on flow rate of small layers and displacement efficiency in parallel linear cores（the permeability was 4，1.5，0.5 μm²，respectively）. The results showed that as the concentration of AP-P4 increased，the viscosity and molecular coil dimension of AP-P4 solution increased，the resistance factor and residual resistance factor also increased under similar permeability. When concentrations of AP-P4 was 1500 mg/L，1750 mg/L and 2000 mg/L，respectively，the corresponding permeability limits was 1150 × 10^-3 μm²、1500 × 10^-3 μm² and 1780 × 10^-3 μm²，respectively. The change of polymer concentration affected not only the time of profile inversion but also the displacement ability of polymer in all small layers. When polymer concentration ranged in 1500—2000 mg/L，with the concentration increasing，the adaptation between hydrophobic associating polymer and reservoir heterogeneity got worse，the affected area of medium and low permeability layer got smaller and profile inversion time moved up，and the oil recovery firstly increased then decreased.Displacement efficiency reached the best at the concentration of 1750 mg/L，indicating that the adaptation between hydrophobic associating polymer and reservoir heterogeneity is very important to oil recovery.

Abstract:According to Daqing Lamadian reservoir geology and fluid properties as the research object, the composition of polymer and surfactant (SP) binary complex system and its effect on oil displacement were studied. The results showed that under the condition of equal reagent cost and fixing polymer concentration (2200 mg/L), the apparent viscosity of oil displacement agent and the interfacial tension increased with increasing surfactant concentration and decreasing alkali concentration in appropriate concentration range. Compared with ASP(alkali/surfactant/polymer) ternary compound system, the resistance coefficient and residual resistance coefficient of SP binary compound system was larger, and the ability of fluid diversion was stronger. But when the surfactant concentration was too high (2.0%), the resistance coefficient and residual resistance coefficient would decrease. When the surfactant mass fraction increased from 0.5% to 5.0%, the enhanced oil recovery rate of SP system increased first and then decreased, and the maximum value 22.5% appeared with 1.5% surfactant dosage, the output/input ratio decreased from 6.7 to 0.8. When the surfactant dosage was 0.5%—1.5%, the economic effect of SP binary flooding technical was better. When the quantity of alkali increased from 0.4% to 1.2%, the enhanced oil recovery rate of poly/alkali binary compound flooding decreased from 14.2% to 9.9%. The optimum formula of SP binary complex system was 2000 mg/L polymer and 0.5%—1.5% surfactant.

Abstract:This work focused on the effects of concentrations of alkali Na₂CO₃，nonionic surfactant BJN-01 and inorganic salt on the dewatering ratios and the apparent viscosities of heavy oil-in-water emulsions. The action laws and synergistic reaction mechanism of the compound systems on the stabilities and rheological properties of emulsion were analyzed. The results showed that the emulsion with 500 mg/L alkali concentration and 0.5% emulsifier volume fraction was the most stable，and its dewatering ratio was 60.7% after standing for 19 h at room temperature. Furthermore，its apparent viscosity was lower，which was 86.2 mPa·s at 30℃ and 20.4 s-1. But adding NaCl into the system could reduce the stability of the emulsion. The higher salt concentration，the greater dewatering ratio was. For the system with 0.5% emulsifier volume fraction and 500—6000 mg/L alkali，the stability of emulsion decreased and its apparent viscosity increased with increasing dosage of alkali. However，for the system with 500 mg/L alkali and 0.5%—0.9% emulsifier volume fraction，the stability of emulsion strengthened and its apparent viscosity increased with increasing dosage of emulsifier.

Abstract:The viscosity of ASP system and the interfacial tension between ASP system and the crude oil can be changed when the ASP agent flows through the Secondary-Class oil layer. In this paper, five different length of artificial cores（10 cm，20 cm，30 cm，60 cm，80cm）were used to simulate the different ASP migration distances. The viscosity of the production fluid and the interfacial tension between the production fluid and the simulated oil were measured in order to analysis the effect of the change of ASP agent properties on recovery. The result showed that as the migration distance increasing, the ASP flooding recovery decreased gradually and the decreasing range of the recovery was larger nearby the injection end. The ASP flooding recovery was affected by the viscosity and the interfacial tension. When the migration distance was smaller than 30 cm, the displacement efficient and sweep efficient were relative higher because of the low interfacial tension and strong mobility control ability, leading to higher flooding recovery and ultimate recovery; however, when the migration distance was larger than 30 cm, the viscosity played the dominant role in the ASP flooding process and the effect of the interfacial tension was weak. The ASP flooding recovery increased with the increase of relative injection volume. Therefore, the increase of the relative injection volume of the ASP flooding adequately could enhance the recovery of Daqing Second-Class oil layer effectively.

Abstract:The main factors that affected the viscosity reduction of the polymer solution prepared with Chengdong sewage from Shengli Oilfield were studied through the orthogonal analysis. Taking into consideration of the main factors from Chengdong sewage, the viscosity increasing agent was developed, the viscosity of polymer solution prepared with treated sewage could be increased from 12 mPa·s to 32 mPa·s, increasing by 167%; The increasing -viscosity mechanism could be analyzed by AFM and DLS , on the one hand, the method of precipitation with NaOH could eliminate the impact on polymer aggregates from Fe²⁺, and the particle size of polymer aggregates increased from 80.5 nm to 159.9 nm; on the other hand, Ca²⁺, Mg²⁺ could be shielded by the ion shield agent ,so that the crimp effect of polymer molecular chain from Ca²⁺, Mg²⁺ was reduced; and polymer aggregates size increased from 160.1 nm to 208.5 nm.

Abstract:Chemical demulsification method is effective for treating waste oil base drilling fluid，but the lack of special demulsifier has limited its application in the field. In this paper，a special waste oil-based drilling fluid demulsifier，named as ZYFYP，which consistd of AE8051，BP-169，AP-05 and OP-10，had been developed. The effect of ZYFYP in treating waste oil-based drilling fluid of Jiao-51 Well was remarkable during demulsification-flocculation-separation treatment process. Under the condition of ZYFYP amount of 0.8%（mass ratio of AE8051，BP-169，AP-05，OP-10 of 3:2:1:3），flocculant agent PAM amount of 0.2%，surfactant OT-15 amount of 1.2%，dispersant Na₅P₃O₁₀ amount of 10%，the oil recovery rate was 98.6% after centrifuge separation for 5 minitues at the speed of 3500 r/min and at the temperature of 15—50℃. ZYFYP was suitable for treating different density waste oil-based drilling fluid in solid-liquid separation process. Heating process was not needed，equipment requirement was not high and the cost was low，the oil recovery rate from waste oil-based drilling fluid was greater than 96%.

Abstract:Water-assisted solvent extraction method was used to recovery qualified oil from oily sludge. Based on the solubility parameter and“rule of similarity”，several efficient solvents were selected. Through the mixture of solvent to adjust the solubility parameter researchers developed a highly efficient，harmfulless and environmental friendly extracting solvent. The extracting solvent consisted of hexane（A2），mixed naphthenes（A3）and alcohol ether mixture（B1）. The volume ratio of A2∶A3∶B1 was 0.5∶0.3∶0.2. The influence of ratio of solvent to mud，extracting temperature，extracting time and stirring rate on the effect of extraction was studied. The results showed that the optimum extraction condition was obtained as follows：5∶1 ratio of solvent to mud，35℃ extraction temperature，45 min extraction time，160 r/min stirring speed. The residual oil rate of crude oil was 3.65% under the optimum extraction condition. The extracting solvent had good oil removing rate，the interface of oil and water became very obvious without emulsification and the water could separate from oil easily. The crude oil fractions over 350℃ accounted for 74%，which indicated that crude oil was heavier. The content of saturates，aromatics，resins，asphaltenes，S and Ni was 7.54%， 45.13%，28.12%，5.23%，1.99% and 622 μg/g. The water content of oil extracted was 0.8% and reached the requirements of oil transportation.

Abstract:The methods of interfacial modification in tight reservoirs were summarized. And the micro mechanism of interfacial modification was analyzed. The effects of interfacial modification by fluoride on seepage in tight sandstone reservoirs and its application in oil and gas fields were introduced. Finally，the application prospects of interface modification and further study in reservoir damage control and production were proposed.

Abstract:The composition of clean fracturing fluid and the thickening and gel breaking mechanism of clean fracturing fluid was introduced. The theoretical basis，system composition，research progress and application situation of clean fracturing fluids at home and abroad were summarized. Through summarizing the problems in indoor research and field application，the development trend of the clean fracturing fluid was put forward，namely to improve the heat-resistant ability of clean fracturing fluid，to control cost，to reduce the fluid loss，to improve the gel breaking performance on the basis of ensurring clean fracturing fluid properties.

Abstract:Silicate water shutoff agent system，chemical shutoff technology and its application examples were reviewed. The silicate water shutoff agent system was divided into four types，such as silicate gel water shutoff agent system，silicate precipitation water shutoff agent system，mixed silicate water shutoff agent system and particle silicate water shutoff agent system. The silicate chemical shutoff technology was divided into three types，including single fluid shutoff method，double fluid shutoff method and mixed slug shutoff method. The effect of silicate chemical water shutoff technology in Jidong，Daqing and Tahe oilfield was introduced. The research suggestions and prospects of silicate chemical water shutoff technology were put forward.

Abstract:With the acceleration of exploration speed and the upgrade of environment protect requirement，the disposement and use of the oily sludge has become an urgent problem for every oilfield and petroleum company. In this article，the present situation about domestic and foreign oily sludge treatment technology was summarized，such as solvent extraction，chemical cleaning，conditioning-mechanical separation，pyrolysis，ultrasonic，microwave，reinjection/profile，electrokinetic and freeze/thaw. In addition，a comparative analysis of the flow features and process is then undertaken with each of these treatments. What’s more，combined with the actual situation，the current situation and development of oily sludge treatment in Yanchang oilfield were analyzed.