Study on Viscosity Reducing and Oil Displacement Agent for Water-Flooding Heavy Oil Reservoir

In the process of water-flooding development of heavy oil reservoir,due to the high viscosity and oil-water mobility ratio of heavy oil,there are some problems such as poor fluidity,high residual oil saturation and low recovery efficiency,which seriously restrict the efficient development of heavy oil.The molecular structure characteristics of asphaltenes and resins in heavy oil were analyzed.Based on the three most concerned properties of chemical agents,including the emulsification performance,the interface performance and the oil washing performance,three chemical oil displacement agents for heavy oil reservoirs were developed,and the structure of the chemical agents were characterized by high resolution mass spectrometry.The performance evaluation of chemical agents and core displacement experiments show that there is no obvious correlation between the properties of chemical agents,including interfacial tension,emulsifying ability and oil washing ability.For heavy oil reservoirs,the emulsification and viscosity reduction performance of chemical agents was more important than the oil washing capacity,and the oil washing capacity was more important than the interface performance.Viscosity reduction performance was the key parameter of oil displacement agent suitable for heavy oil reservoir.The composite binary system consisting of the viscosity reducer and the polymer had better oil recovery than using viscosity reducer alone.

Evaluation of the injection and plugging ability of a novel epoxy resin in cement cracks

Sustained casing pressure(SCP)is a crucial issue in the oil and gas production lifecycle.Epoxy resins,exhibiting exceptional compressive strength,ductility,and shear bonding strength,have the potential to form reliable barriers.The injectivity and sealing capacity of the epoxy resin is crucial parameters for the success of shallow remediation operations.This study aimed to develop and assess a novel solid-free resin sealant as an alternative to Portland cement for mitigating fluid leakage.The investigation evaluated the viscosity,compressive strength,and brittleness index of the epoxy resin sealant,as well as its tangential and normal shear strengths in conjunction with casing steel.The flow characteristics and sealing abilities of conventional cement and epoxy resin were comparatively analyzed in cracks.The results showed that the application of a viscosity reducer facilitated control over the curing time of the epoxy resin,ranging from 1.5 to 6 h,and reduced the initial viscosity from 865.53 to 118.71 m Pa,s.The mechanical properties of the epoxy resin initially increased with a rise in curing agent content before experiencing a minor decrease.The epoxy resin containing 30%curing agent exhibited optimal mechanical properties.After a 14-day curing period,the epoxy resin's compressive strength reached81.37 MPa,2.12 times higher than that of cement,whereas the elastic modulus of cement was 2.99 times greater than that of the epoxy resin.The brittleness index of epoxy resin is only 3.42,demonstrating high flexibility and toughness.The tangential and normal shear strengths of the epoxy resin exceeded those of cement by 3.17 and 2.82 times,respectively.In a 0.5 mm-wide crack,the injection pressure of the epoxy resin remained below 0.075 MPa,indicating superior injection and flow capabilities.Conversely,the injection pressure of cement surged dramatically to 2.61 MPa within 5 min.The breakthrough pressure of0.5 PV epoxy resin reached 7.53 MPa,decreasing the crack's permeability to 0.02 D,a mere 9.49%of the permeability observed following cement plugging.Upon sealing a 2 mm-wide crack using epoxy resin,the maximum breakthrough pressure attained 5.47 MPa,3.48 times of cement.These results suggest that epoxy resin sealant can be employed safely and effectively to seal cracks in the cement.

Synthesis and evaluation of an oil-soluble viscosity reducer for heavy oil

To reduce the viscosity of highly-viscous oil of the Tahe oilfield （Xinjiang,China）,an oilsoluble polybasic copolymer viscosity reducer for heavy oil was synthesized using the orthogonal method.The optimum reaction conditions are obtained as follows：under the protection of nitrogen,a reaction time of 9 h,monomer mole ratio of reaction materials of 3：2：2 （The monomers are 2-propenoic acid,docosyl ester,maleic anhydride and styrene,respectively）,initiator amount of 0.8% （mass percent of the sum of all the monomers） and reaction temperature of 80 oC.This synthesized viscosity reducer is more effective than commercial viscosity reducers.The rate of viscosity reduction reached 95.5% at 50 oC.Infrared spectra （IR） and interfacial tensions of heavy oil with and without viscosity reducer were investigated to understand the viscosity reduction mechanism.When viscosity reducer is added,the molecules of the viscosity reducer are inserted amongst the molecules of crude oil,altering the original intermolecular structure of crude oil and weakening its ability to form hydrogen bonds with hydroxyl or carboxyl groups,so the viscosity of crude oil is reduced.Field tests of the newly developed oil-soluble viscosity reducer was carried out in the Tahe Oilfield,and the results showed that 44.5% less light oil was needed to dilute the heavy oil to achieve the needed viscosity.

PROPERTIES OF DILUTE SOLUTIONS OF HYDROPHOBICALLY MODIFIED POLY (4-VINYL PYRIDINE) (POLYSOAPS)

Hydrophobically modified poly(4-vinyl pyridines) by alkyl bromides are kinds of polysoap similar to the surfactant. Properties of dilute solutions were studied through the viscosity measurements in pure water and NaCl solutions. In aqueous solutions of polysoaps hydrophobic interaction can be attributed to aggregation of hydrophobic groups of the polysoap main chains. The hydrophobic groups of polysoap can aggregate to form hydrophobic microdomains (micelles) in aqueous solution. This is a compact conformation. The formation of such microdomains is a process of dynamic equilibrium.