Research on thermal insulation materials properties under HTHP conditions for deep oil and gas reservoir rock ITP-Coring

Deep oil and gas reservoirs are under high-temperature conditions,but traditional coring methods do not consider temperature-preserved measures and ignore the influence of temperature on rock porosity and permeability,resulting in distorted resource assessments.The development of in situ temperaturepreserved coring(ITP-Coring)technology for deep reservoir rock is urgent,and thermal insulation materials are key.Therefore,hollow glass microsphere/epoxy resin thermal insulation materials(HGM/EP materials)were proposed as thermal insulation materials.The materials properties under coupled hightemperature and high-pressure(HTHP)conditions were tested.The results indicated that high pressures led to HGM destruction and that the materials water absorption significantly increased;additionally,increasing temperature accelerated the process.High temperatures directly caused the thermal conductivity of the materials to increase;additionally,the thermal conduction and convection of water caused by high pressures led to an exponential increase in the thermal conductivity.High temperatures weakened the matrix,and high pressures destroyed the HGM,which resulted in a decrease in the tensile mechanical properties of the materials.The materials entered the high elastic state at 150℃,and the mechanical properties were weakened more obviously,while the pressure led to a significant effect when the water absorption was above 10%.Meanwhile,the tensile strength/strain were 13.62 MPa/1.3%and 6.09 MPa/0.86%at 100℃ and 100 MPa,respectively,which meet the application requirements of the self-designed coring device.Finally,K46-f40 and K46-f50 HGM/EP materials were proven to be suitable for ITP-Coring under coupled conditions below 100℃ and 100 MPa.To further improve the materials properties,the interface layer and EP matrix should be optimized.The results can provide references for the optimization and engineering application of materials and thus technical support for deep oil and gas resource development.

Phase Transitions and Seepage Characteristics during the Depletion Development of Deep Condensate Gas Reservoirs

Deep condensate gas reservoirs exhibit highly complex and variable phase behaviors,making it crucial to understand the relationship between fluid phase states and flow patterns.This study conducts a comprehensive analysis of the actual production process of the deep condensate gas well A1 in a certain oilfield in China.Combining phase behavior analysis and CMG software simulations,the study systematically investigates phase transitions,viscosity,and density changes in the gas and liquid phases under different pressure conditions,with a reservoir temperature of 165°C.The research covers three crucial depletion stages of the reservoir:single-phase flow,two-phase transition,and two-phase flow.The findings indicate that retrograde condensation occurs when the pressure falls below the dew point pressure,reachingmaximum condensate liquid production at around 25MPa.As pressure decreases,gas phase density and viscosity gradually decrease,while liquid phase density and viscosity show an increasing trend.In the initial single-phase flow stage,maintaining a consistent gas-oil ratio is observed when both bottom-hole and reservoir pressures are higher than the dew point pressure.However,a sudden drop in bottom-hole pressure below the dew point triggers the production of condensate oil,significantly reducing subsequent gas and oil production.In the transitional two-phase flow stage,as the bottom-hole pressure further decreases,the reservoir exhibits a complex flow regime with coexisting areas of gas and liquid.In the subsequent two-phase flow stage,when both bottom-hole and reservoir pressures are below the dew point pressure,a significant increase in the gas-oil ratio is observed.The reservoir manifests a two-phase flow regime,devoid of single-phase gas flow areas.For lowpressure conditions in deep condensate gas reservoirs,considerations include gas injection,gas lift,and cyclic gas injection and production in surrounding wells.Additionally,techniques such as hot nitrogen or CO_(2) injection can be employed to mitigate retrograde condensation damage.The implications of this study are crucial for developing targeted development strategies and enhancing the overall development of deep condensate gas reservoirs.

Formation condition of deep gas reservoirs in tight sandstones in Kuqa Foreland Basin

Due to the high expense of deep oil and gas exploration,prediction of gas-bearing properties before drilling is crucial for deep gas reservoir of tight sandstone.Deep tight sandstone gas fields in Kuqa Foreland Basin are characterized by high abundance,high gas saturation,high pressure,high and stable yield,which belong to high-efficiency tight gas reservoir.Based on theoretical analysis of controlling factors and mechanisms of gas-bearing properties for tight sandstone gas reservoir,and taking tight sandstone gas fields with high effectiveness such as Dibei,Keshen and Dibei gas fields in Kuqa Foreland Basin as examples,formation condition and mechanism of high-efficiency tight sandstone gas reservoir in Kuqa area are studied through a comparative analysis of typical tight sandstone gas reservoir in Sichuan Basin and Ordos Basin.The results show that the formation condition of deep gas reservoir of tight sandstone in Kuqa foreland basin includes four factors:i.e.,overpressure gas charging,fracture development,“early-oil and late-gas”accumulation process and favorable preservation condition.The overpressure gas charging and fracture development are the most important factors for formation of high-efficiency tight gas reservoirs in Kuqa Foreland Basin.High-quality source rocks,high sourcereservoir pressure difference,and overpressure filling induced thereby are preconditions for formation of tight sandstone with high gas saturation.The fracture development controls gas migration,accumulation,and high yield of tight sandstone gas reservoir.The reservoir wettability changed by the early oil charging is beneficial to late natural gas charging,and the preservation condition of high-quality gypsum cap rocks is the key factor for gas reservoirs to maintain overpressure and high gas saturation.Matching of above four favorable factors leads to the tight sandstone gas reservoir with high abundance,high gas saturation and high gas production in Kuqa Foreland Basin,which is very different from other basins.Under the condition of little difference in physical property of tight sandstone reservoir,excessive source-reservoir pressure difference,facture development,preservation condition and current formation overpressure are the most significant factors to be considered in exploration and evaluation of deep tight sandstone gas.

Factors controlling the formation and evolution of source rocks in the Shahezi Formation,Xujiaweizi fault depression,Songliao Basin

The types and quality of source rocks in the Shahezi Formation are the key factors affecting the distributions of various deep gas reservoirs in the Xujiaweizi fault depression in Songliao Basin.To clarify the quality differences and origins of different types of source rocks in the Shahezi Formation,this study reconstructed the sedimentary and water environment,determined the controlling effects of fault activity,sedimentary facies,and paleo-sedimentary environment on the quality of various source rocks,by making full use of seismic,logging,core,organic geochemical and element geochemical analysis.The results show that two types of source rocks developed in the Shahezi Formation,namely,mudstones and coals.The mudstones have a relatively high abundance of organic matter,which consists of type-Ⅱ kerogen and partial type-Ⅲ kerogen,and are concentrated in Sha-I Member.The coals have a high abundance of organic matter,which consist of type-Ⅲ kerogen,and are mainly distributed in Sha-Ⅱ Member.During the deposition of Sha-I Member,intense fault activity formed arrow,deep-water lacustrine basins with high salinity and strong reducibility on the downthrow sides of faults.During the deposition of Sha-II Member,fault activity progressively weakened,and the areas of lacustrine basins enlarged to their maximum values and became wide,shallow-water basins with low salinity and low reducibility.The development of source rocks was controlled by fault activity,sedimentary facies,and paleo-sedimentary environment.Fault activity formed accommodation space on the downthrown sides of faults for mudstone accumulation,thus determining mudstone thickness.The sedimentary environment controlled the organic matter input and determined the distribution of mudstones and coals.The paleo-sedimentary environment,which consisted of paleo-salinity,as well as paleo-water depth and redox conditions,affected the accumulation and preservation of organic matter and is the main controlling factor for the quality difference of various source rocks in the Shahezi Formation.