Development and technology status of energy storage in depleted gas reservoirs

Utilizing energy storage in depleted oil and gas reservoirs can improve productivity while reducing power costs and is one of the best ways to achieve synergistic development of"Carbon Peak–Carbon Neutral"and"Underground Resource Utiliza-tion".Starting from the development of Compressed Air Energy Storage(CAES)technology,the site selection of CAES in depleted gas and oil reservoirs,the evolution mechanism of reservoir dynamic sealing,and the high-flow CAES and injection technology are summarized.It focuses on analyzing the characteristics,key equipment,reservoir construction,application scenarios and cost analysis of CAES projects,and sorting out the technical key points and existing difficulties.The devel-opment trend of CAES technology is proposed,and the future development path is scrutinized to provide reference for the research of CAES projects in depleted oil and gas reservoirs.

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.

Fine quantitative characterization of high-H2S gas reservoirs under the influence of liquid sulfur deposition and adsorption

In order to clarify the influence of liquid sulfur deposition and adsorption to high-H2S gas reservoirs,three types of natural cores with typical carbonate pore structures were selected for high-temperature and high-pressure core displacement experiments.Fine quantitative characterization of the cores in three steady states(original,after sulfur injection,and after gas flooding)was carried out using the nuclear magnetic resonance(NMR)transverse relaxation time spectrum and imaging,X-ray computer tomography(CT)of full-diameter cores,basic physical property testing,and field emission scanning electron microscopy imaging.The loss of pore volume caused by sulfur deposition and adsorption mainly comes from the medium and large pores with sizes bigger than 1000μm.Liquid sulfur has a stronger adsorption and deposition ability in smaller pore spaces,and causes greater damage to reservoirs with poor original pore structures.The pore structure of the three types of carbonate reservoirs shows multiple fractal characteristics.The worse the pore structure,the greater the change of internal pore distribution caused by liquid sulfur deposition and adsorption,and the stronger the heterogeneity.Liquid sulfur deposition and adsorption change the pore size distribution,pore connectivity,and heterogeneity of the rock,which further changes the physical properties of the reservoir.After sulfur injection and gas flooding,the permeability of TypeⅠreservoirs with good physical properties decreased by 16%,and that of TypesⅡandⅢreservoirs with poor physical properties decreased by 90%or more,suggesting an extremely high damage.This indicates that the worse the initial physical properties,the greater the damage of liquid sulfur deposition and adsorption.Liquid sulfur is adsorbed and deposited in different types of pore space in the forms of flocculence,cobweb,or retinitis,causing different changes in the pore structure and physical property of the reservoir.

Electrical structure identification of deep shale gas reservoir in complex structural area using wide field electromagnetic method

To fully exploit the technical advantages of the large-depth and high-precision artificial source electromagnetic method in the complex structure area of southern Sichuan and compensate for the shortcomings of the conventional electromagnetic method in exploration depth,precision,and accuracy,the large-depth and high-precision wide field electromagnetic method is applied to the complex structure test area of the Luochang syncline and Yuhe nose anticline in the southern Sichuan.The advantages of the wide field electromagnetic method in detecting deep,low-resistivity thin layers are demonstrated.First,on the basis of the analysis of physical property data,a geological–geoelectric model is established in the test area,and the wide field electromagnetic method is numerically simulated to analyze and evaluate the response characteristics of deep thin shale gas layers on wide field electromagnetic curves.Second,a wide field electromagnetic test is conducted in the complex structure area of southern Sichuan.After data processing and inversion imaging,apparent resistivity logging data are used for calibration to develop an apparent resistivity interpretation model suitable for the test area.On the basis of the results,the characteristics of the electrical structure change in the shallow longitudinal formation of 6 km are implemented,and the transverse electrical distribution characteristics of the deep shale gas layer are delineated.In the prediction area near the well,the subsequent data verification shows that the apparent resistivity obtained using the inversion of the wide field electromagnetic method is consistent with the trend of apparent resistivity revealed by logging,which proves that this method can effectively identify the weak response characteristics of deep shale gas formations in complex structural areas.This experiment,it is shown shows that the wide field electromagnetic method with a large depth and high precision can effectively characterize the electrical characteristics of deep,low-resistivity thin layers in complex structural areas,and a new set of low-cost evaluation technologies for shale gas target layers based on the wide field electromagnetic method is explored.

Gas-Water Production of a Continental Tight-Sandstone Gas Reservoir under Different Fracturing Conditions

A numerical model of hydraulic fracture propagation is introduced for a representative reservoir(Yuanba continental tight sandstone gas reservoir in Northeast Sichuan).Different parameters are considered,i.e.,the interlayer stress difference,the fracturing discharge rate and the fracturing fluid viscosity.The results show that these factors affect the gas and water production by influencing the fracture size.The interlayer stress difference can effectively control the fracture height.The greater the stress difference,the smaller the dimensionless reconstruction volume of the reservoir,while the flowback rate and gas production are lower.A large displacement fracturing construction increases the fracture-forming efficiency and expands the fracture size.The larger the displacement of fracturing construction,the larger the dimensionless reconstruction volume of the reservoir,and the higher the fracture-forming efficiency of fracturing fluid,the flowback rate,and the gas production.Low viscosity fracturing fluid is suitable for long fractures,while high viscosity fracturing fluid is suitable for wide fractures.With an increase in the fracturing fluid viscosity,the dimensionless reconstruction volume and flowback rate of the reservoir display a non-monotonic behavior,however,their changes are relatively small.

Evaluation of Well Spacing for Primary Development of Fractured Horizontal Wells in Tight Sandstone Gas Reservoirs

Methods for horizontal well spacing calculation in tight gas reservoirs are still adversely affected by the complexity of related control factors,such as strong reservoir heterogeneity and seepage mechanisms.In this study,the stress sensitivity and threshold pressure gradient of various types of reservoirs are quantitatively evaluated through reservoir seepage experiments.On the basis of these experiments,a numerical simulation model(based on the special seepage mechanism)and an inverse dynamic reserve algorithm(with different equivalent drainage areas)were developed.The well spacing ranges of Classes I,II,and III wells in the Q gas field are determined to be 802–1,000,600–662,and 285–400 m,respectively,with their average ranges as 901,631,and 342.5 m,respectively.By considering both the pairs of parallel well groups and series well groups as examples,the reliability of the calculation results is verified.It is shown that the combination of the two models can reduce errors and provide accurate results.

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.

Numerical Simulation of Oil and Gas Two-Phase Flow in Deep Condensate Gas Reservoirs in Bohai Buried Hills

The BZ19-6 gas field is characterized by high temperature and high pressure (HTHP), high condensate content, little difference between the formation pressure and dew point pressure, and large amount of reverse condensate liquid. During the early stage of depletion development, the production gas-oil ratio (GOR) and production capacity remain relatively stable, which is inconsistent with the conventional reverse condensate seepage law. In view of the static and dynamic conflict in development and production, indoor high-temperature and high-pressure PVT experiment was carried out to reveal the mist-like condensation phenomenon of fluids in the BZ19-6 formation. And the seepage characteristics of condensate gas reservoirs with various degrees of depletion under the condition of HTHP were analyzed based on production performance. The change rule of fluid phase state was analyzed in response to the characterization difficulties of the seepage mechanism. The fluid state was described using the miscible mechanism. And the interphase permeability interpolation coefficient was introduced based on interfacial tension. By doing so, the accurate characterization of the “single-phase flow of condensate gas-near-miscible mist-like quasi single-phase flow-oil-gas two-phase flow” during the development process was achieved. Then the accurate fitting of key indicators for oilfield development was completed, and the distribution law of formation pressure and the law of condensate oil precipitation under different reservoir conditions are obtained. Based on research results, the regulation strategy of variable flow rate production was developed. Currently, the work system has been optimized for 11 wells, achieving a “zero increase” in the GOS of the gas field and an annual oil increase of 22,000 cubic meters.

Salt-Lake Basin Bedrock Weathered Crust Gas Reservoir in the Altun Mountains Front of the Qaidam Basin,Western China

The bedrock weathered crust in front of the Altun Mountains in the Qaidam Basin,western China,is different from others because this is a salt-lake basin,where saline water fluid infiltrates and is deposited in the overlying strata.A large amount of gypsum infills the bedrock weathered crust,and this has changed the pore structure.Using core observation,polarized light microscopy,electron probe,physical property analysis and field emission scanning electron microscopy experiments,the characteristics of the weathered bedrock have been studied.There are cracks and a small number of dissolved pores in the interior of the weathered crust.Matrix micropores are widely developed,especially the various matrix cracks formed by tectonics and weathering,as well as the stress characteristics of small dissolved pores,and physical properties such as porosity and permeability.This‘dual structure’developed in the bedrock is important for guiding the exploration of the lake basin bedrock for natural gas.

Investigation of influence factors on CO_(2) flowback characteristics and optimization of flowback parameters during CO_(2) dry fracturing in tight gas reservoirs

CO_(2) dry fracturing is a promising alternative method to water fracturing in tight gas reservoirs,especially in water-scarce areas such as the Loess Plateau.The CO_(2) flowback efficiency is a critical factor that affects the final gas production effect.However,there have been few studies focusing on the flowback characteristics after CO_(2) dry fracturing.In this study,an extensive core-to-field scale study was conducted to investigate CO_(2) flowback characteristics and CH_(4) production behavior.Firstly,to investigate the impact of core properties and production conditions on CO_(2) flowback,a series of laboratory experiments at the core scale were conducted.Then,the key factors affecting the flowback were analyzed using the grey correlation method based on field data.Finally,taking the construction parameters of Well S60 as an example,a dual-permeability model was used to characterize the different seepage fields in the matrix and fracture for tight gas reservoirs.The production parameters after CO_(2) dry fracturing were then optimized.Experimental results demonstrate that CO_(2) dry fracturing is more effective than slickwater fracturing,with a 9.2%increase in CH_(4) recovery.The increase in core permeability plays a positive role in improving CH_(4) production and CO_(2) flowback.The soaking process is mainly affected by CO_(2) diffusion,and the soaking time should be controlled within 12 h.Increasing the flowback pressure gradient results in a significant increase in both CH_(4) recovery and CO_(2) flowback efficiency.While,an increase in CO_(2) injection is not conducive to CH_(4) production and CO_(2) flowback.Based on the experimental and field data,the important factors affecting flowback and production were comprehensively and effectively discussed.The results show that permeability is the most important factor,followed by porosity and effective thickness.Considering flowback efficiency and the influence of proppant reflux,the injection volume should be the minimum volume that meets the requirements for generating fractures.The soaking time should be short which is 1 day in this study,and the optimal bottom hole flowback pressure should be set at 10 MPa.This study aims to improve the understanding of CO_(2) dry fracturing in tight gas reservoirs and provide valuable insights for optimizing the process parameters.

Study of the Seepage Mechanism in Thick Heterogeneous Gas Reservoirs

The seepage mechanism plays a crucial role in low-permeability gas reservoirs.Compared with conventional gas reservoirs,low-permeability sandstone gas reservoirs are characterized by low porosity,low permeability,strong heterogeneity,and high water saturation.Moreover,their percolation mechanisms are more complex.The present work describes a series of experiments conducted considering low-permeability sandstone cores under pressuredepletion conditions(from the Xihu Depression in the East China Sea Basin).It is shown that the threshold pressure gradient of a low-permeability gas reservoir in thick layers is positively correlated with water saturation and negatively correlated with permeability and porosity.The reservoir stress sensitivity is related to permeability and rock composition.Stress sensitivity is generally low when permeability is high or in the early stage of gas reservoir development.It is also shown that in sand conglomerates,especially the more sparsely filled parts,the interstitial materials among the conglomerates can be rapidly dislodged from the skeleton particles under stress.This material can therefore disperse,migrate,and block the pore throat producing serious,stress-sensitive damage.

Proppant transport in rough fractures of unconventional oil and gas reservoirs

A method to generate fractures with rough surfaces was proposed according to the fractal interpolation theory.Considering the particle-particle,particle-wall and particle-fluid interactions,a proppant-fracturing fluid two-phase flow model based on computational fluid dynamics(CFD)-discrete element method(DEM)coupling was established.The simulation results were verified with relevant experimental data.It was proved that the model can match transport and accumulation of proppants in rough fractures well.Several cases of numerical simulations were carried out.Compared with proppant transport in smooth flat fractures,bulge on the rough fracture wall affects transport and settlement of proppants significantly in proppant transportation in rough fractures.The higher the roughness of fracture,the faster the settlement of proppant particles near the fracture inlet,the shorter the horizontal transport distance,and the more likely to accumulate near the fracture inlet to form a sand plugging in a short time.Fracture wall roughness could control the migration path of fracturing fluid to a certain degree and change the path of proppant filling in the fracture.On the one hand,the rough wall bulge raises the proppant transport path and the proppants flow out of the fracture,reducing the proppant sweep area.On the other hand,the sand-carrying fluid is prone to change flow direction near the contact point of bulge,thus expanding the proppant sweep area.

Stress sensitivity of carbonate gas reservoirs and its microscopic mechanism

In order to evaluate the stress sensitivity of carbonate reservoirs,a series of rock stress sensitivity tests were carried out under in-situ formation temperature and stress condition.Based on the calibration of capillary pressure curve,the variable fractal dimension was introduced to establish the conversion formula between relaxation time and pore size.By using the nuclear magnetic resonance(NMR)method,the pore volume loss caused by stress sensitivity within different scales of pore throat was quantitatively analyzed,and the microscopic mechanism of stress sensitivity of carbonate gas reservoirs was clarified.The results show that fractures can significantly affect the stress sensitivity of carbonate reservoirs.With the increase of initial permeability,the stress sensitivity coefficient decreases and then increases for porous reservoirs,but increases monotonously for fractured-porous reservoirs.The pore volume loss caused by stress sensitivity mainly occurs for mesopores(0.02–0.50μm),contributing more than 50%of the total volume loss.Single high-angle fracture contributes 9.6%of the stress sensitivity and 15.7%of the irreversible damage.The microscopic mechanism of the stress sensitivity of carbonate gas reservoirs can be concluded as fracture closure,elastic contraction of pores and plastic deformation of rock skeleton.

Simulation of Gas-Water Two-Phase Flow in Tight Gas Reservoirs Considering the Gas Slip Effect

A mathematical model for the gas-water two-phase flow in tight gas reservoirs is elaborated.The model can account for the gas slip effect,stress sensitivity,and high-speed non-Darcy factors.The related equations are solved in the framework of a finite element method.The results are validated against those obtained by using the commercial software CMG(Computer Modeling Group software for advanced recovery process simulation).It is shown that the proposed method is reliable.It can capture the fracture rejection characteristics of tight gas reservoirs better than the CMG.A sensitivity analysis of various control factors(initial water saturation,reservoir parameters,and fracturing parameters)affecting the production in tight gas wells is conducted accordingly.Finally,a series of theoretical arguments are provided for a rational and effective development/exploitation of tight sandstone gas reservoirs.

Simulation of the Production Performances of Horizontal Wells with a Fractured Shale Gas Reservoir

The production performances of a well with a shale gas reservoir displaying a complex fracture network are simulated.In particular,a micro-seismic cloud diagram is used to describe the fracture network,and accordingly,a production model is introduced based on a multi-scale flow mechanism.A finite volume method is then exploited for the integration of the model equations.The effects of apparent permeability,conductivity,Langmuir volume,and bottom hole pressure on gas well production are studied accordingly.The simulation results show that ignoring the micro-scale flow mechanism of the shale gas leads to underestimating the well gas production.It is shown that after ten years of production,the cumulative gas production difference between the two scenarios with and without considering the micro-scale flow mechanisms is 19.5%.The greater the fracture conductivity,the higher the initial gas production of the gas well and the cumulative gas production.The larger the Langmuir volume,the higher the gas production rate and the cumulative gas production.With the reduction of the bottom hole pressure,the cumulative gas production increases,but the growth rate gradually decreases.

Surface Loess Susceptibility Anomalies Directly Indicating Oil and Gas Reservoirs

It is a fact that the near surface loess has magnetic susceptibility anomalies in oil and gas areas. Why these anomalies occur and whether they have any significant value for the exploration of oil and gas reservoirs are questions that geophysicists are mostly concerned about and study. We analyze the cause of the formation of surface loess susceptibility anomalies in oil and gas areas, process the observations of the susceptibility of loess samples taken from an oil and gas area in western China with proper mathematical methods, and determine the background value of loess susceptibility. These results are used to determine oil and gas prospect areas with a numeric evaluation factor based on the susceptibility anomalies. Actual oil wells have verified that using the susceptibility anomalies to indicate the location of oil and gas reservoirs is valid.

Influence of the Earth Stress on the Development of Gas Reservoirs

Gas reservoirs are located kilometers deep beneath the earth's surface under great earth stresses, including the overburden stress and the horizontal stress. After a well is drilled, the stress condition around the well bore will be changed. During the development, a pressure funnel forms around the hole, with the rock stress redistributed. In this paper, the influence of the earth stress on the gas reservoir development, including the output, the period of the steady output, the recovery and ratio, is researched thoroughly with the theory of reservoir seepage dynamics and clarified with the calculation method. The research shows that the earth stress produces impacts on the development of a gas reservoir when the stress is great.

Gas reservoir identification by seismic AVO attributes on fluid substitution

Traditionally, fluid substitutions are often conducted on log data for calculating reservoir elastic properties with different pore fluids. Their corresponding seismic responses are computed by seismic forward modeling for direct gas reservoir identification. The workflow provides us with the information about reservoir and seismic but just at the well. For real reservoirs, the reservoir parameters such as porosity, clay content, and thickness vary with location. So the information from traditional fluid substitution just at the well is limited. By assuming a rock physics model linking the elastic properties to porosity and mineralogy, we conducted seismic forward modeling and AVO attributes computation on a three-layer earth model with varying porosity, clay content, and formation thickness. Then we analyzed the relations between AVO attributes at wet reservoirs and those at the same but gas reservoirs. We arrived at their linear relations within the assumption framework used in the forward modeling. Their linear relations make it possible to directly conduct fluid substitution on seismic AVO attributes. Finally, we applied these linear relations for fluid substitution on seismic data and identified gas reservoirs by the cross-plot between the AVO attributes from seismic data and those from seismic data after direct fluid substitution.

Geological Features and Reservoiring Mode of Shale Gas Reservoirs in Longmaxi Formation of the Jiaoshiba Area

This study is based on the sedimentation conditions, organic geochemistry, storage spaces, physical properties, lithology and gas content of the shale gas reservoirs in Longmaxi Formation of the Jiaoshiba area and the gas accumulation mode is summarized and then compared with that in northern America. The shale gas reservoirs in the Longmaxi Formation in Jiaoshiba have good geological conditions, great thickness of quality shales, high organic content, high gas content, good physical properties, suitable depth, good preservation conditions and good reservoir types. The quality shales at the bottom of the deep shelf are the main target interval for shale gas exploration and development. Shale gas in the Longmaxi Formation has undergone three main reservoiring stages：the early stage of hydrocarbon generation and compaction when shale gas reservoirs were first formed; the middle stage of deep burial and large-scale hydrocarbon generation, which caused the enrichment of reservoirs with shale gas; the late stage of uplift, erosion and fracture development when shale gas reservoirs were finally formed.

Analysis of Reservoir Forming Conditions and Prediction of Continuous Tight Gas Reservoirs for the Deep Jurassic in the Eastern Kuqa Depression,Tarim Basin

The exploration targets in the Kuqa Depression at present are mainly structure traps in Cretaceous-Tertiary.Due to the complexity of mountain distribution and reservoir forming conditions, the exploration of Jurassic in the eastern Kuqa Depression has been in a state of semi-stagnation since the discovery of the Yinan-2 gas reservoir.According to the concept and theory of 'continuous petroleum reservoirs' and the re-analysis of the forming conditions of the Yinan-2 gas reservoir and regional natural gas in the eastern Kuqa Depression,it is believed that the deep Jurassic has good natural gas accumulation conditions as well as geological conditions for forming continuous tight gas reservoirs.The boundary of the Yinan-2 gas reservoir is not controlled by a structural spillpoint.The downdip part of the structure is dominated by gas,while the hanging wall of the fault is filled by water and forming obvious inverted gas and water.The gas reservoir has the normal temperature and ultrahigh pressure which formed in the near source or inner-source.All of these characteristics indicate that the Yinan-2 gas reservoir is different from conventional gas reservoirs.The deep Jurassic in the eastern Kuqa Depression has multisets of source-reservoir-cap assemblages,which comprise interbedded sandstones and mudstones.These assemblages are characterized by a self-generation,self-preserving and self-coverage model.Reservoir sandstones and coal measure mudstones are interbedded with each other at a large scale.As the source rocks,Triassic-Jurassic coal measure mudstones distribute continuously at a large scale and can generate and expel hydrocarbon.Source rocks contact intimately with the overlying sandstone reservoirs.During the late stage of hydrocarbon expulsion,natural gas charged continuously and directly into the neighboring reservoirs.Petroleum migrated mainly in a vertical direction over short distances.With ultra-high pressure and strong charging intensity,natural gas accumulated continuously.Reservoirs are dominated by sandstones of braided delta facies.The sand bodies distribute continuously horizontal.With low porosity and low permeability,the reservoirs are featured by strong heterogeneity.It is hypothesized that the sandstones of the interior depression tend to be relatively tight with increasing depth and structure stress weakness.Thus,it is predicted that continuous tight gas reservoirs of ultra-high pressure may exist in the deep formations of the eastern and even the whole Kuqa Depression.So,it is worth evaluating the exploration potential.