In order to promote the development and utilization of dry hot rock resources in China, we take Kenya OLKARIA block as an example, and introduce the exploration, evaluation, development and utilization process of high temperature geothermal resources in Kenya in detail. At the same time, eight key drilling technologies formed during the development and utilization of high-temperature geothermal resources of the CNPC Great Wall Drilling Company are summarized and detailed engineering examples are listed. At last, the difficulties and challenges encountered in the development and utilization of Kenya's geothermal resources and China's dry hot rock resources are summarized and compared, the similarities and difference between countries are sorted out, and the solutions are put forward. With the establishment of a test base as the core, and with the developing and verifying new technologies and new equipment and forming new technical standards as the research direction, to point out that with the goal of realizing economical, profitable and large-scale development of dry hot rock, to strength basic scientific research work as a means, by the research idea of relying on the support of national policies and strengthen personnel training as the driving force, to provide theoretical and practical guidance for the efficient and economical development of dry hot rock resources in China.

Inorder to further study the vertical distribution characteristics of the shallow geothermal temperature field in the southeastern of Hancheng, Guanzhong Basin. The authors used temperature measuring cable, which is single line multipoint communication, to monitor stratum temperature in a depth of 50 meters for one year in Hancheng. The results shows that the vertical distribution of shallow geothermal temperature is regularity and obviously layered, it can be differentiated as variable temperature zone, constant temperature zone and increased temperature zone. The buried depth of the bottom of variable temperature zone is 15 m, it is significantly affected by climate. Compared with the temperature change of atmosphere, the variable temperature zone has a hysteresis phenomenon. The constant temperature zone depth range is between 15~35 m, and the average temperature is 15.3 ℃, 1.8 ℃ higher than the annual average atmospheric temperature in the same region. The increased temperature zone is below 35 m, and the geothermal gradient is 3.25 ℃/hm within 35~100 m, which is higher than surrounding area. It is concluded that there are three reasons: firstly, the Hancheng fault is heat conduction channel to carry deep heat to shallow formations; secondly, the groundwater runoff intensity is relatively weak to save heat; thirdly, the loose stratum of quaternary and neogene is thick, which can reduce thermal conduction.

The heat exchange technology of the medium-deep buried pipes of the abandoned oil and gas wells is one of the methods of oilfield geothermal development, which is helpful for low-carbon heating in oilfields and reduces the cost of geothermal development. In order to improve the heat transfer of a single well and better guide the reconstruction work, it is necessary to analyze the influencing factors of the heat transfer performance of the geothermal well after reconstruction. In this paper, numerical simulation method is used to analyze the influencing factors of the heat transfer performance of the geothermal well after reconstruction, and the parameters such as geology, well and working conditions are analyzed respectively. The main analysis conclusions are: ① The geothermal gradient and the thermal conductivity of the rock formation in the geological parameters have a great influence on the heat transfer of a single well, and the geological parameters should be the primary consideration factors in the selection of the stimulation target well. ② Well depth, casing outer diameter, and thermal conductivity of central heat exchange tube in the well parameters have certain influence on the heat exchange of a single well, which should be considered when selecting target well and formulating the reconstruction plan. ③ The water temperature and flow rate entering the well in the working condition parameters have an influence on the heat exchange of a single well, and the influence of the working condition parameters should be considered in the design of the surface heat exchange system. The research in this paper has reference significance for the selection of stimulation target wells, the formulation of stimulation plans, and the optimization of operating conditions parameters using the same heat exchange method.

In order to analyze the ground temperature response and thermal effect radius of the heat transfer of the deep buried pipe, a full-scale numerical model of buried pipe heat transfer is established based on the well logging temperature, ground lithology interpretation, and field heat transfer experiments of an actual deep-buried pipe heating project in Xi’an. By the numerical analysis of the heat transfer of the buried pipes in five years, namely five heating periods and four recovery periods, the variation of ground temperature fluctuation （ΔT） around the buried pipe at different depths with running time is summarized. On this basis, by considering the theoretical research and engineering application, three different ΔT limits are selected to determine the thermal effect radius, and the factors affecting the thermal effect radius are analyzed. The results show that when ΔT limit is small enough to close to zero, the thermal effect radius is mainly affected by the geotechnical parameters around the buried pipe, and when ΔT limit increases, the thermal effect radius is mainly affected by ΔT limit.

In order to solve the problem that thermal-hydro-mechanical coupling model of hot-dry-rock（HDR） reservoir fracturing is complex and it is difficult to achieve large-scale multiple cluster of fracturing network simulation, a sequential coupling simulation method of HDR fracturing is proposed. By establishing a fracture expansion thermodynamic solid sequential coupling model of single cluster fracture and multi-cluster fracture network, the thermal-hydro-mechanical sequential coupling simulation of large-scale HDR fracture network is realized. The influence of brittleness index, stress field displacement and other key parameters on the propagation of fracture network are analyzed in this model. The results showed that high temperature difference, large brittleness index and large injection pumpage could promote the propagation of fracture network, but large stress difference is not conducive to the propagation of fracture network.

After more than 50 years of exploration and development, W gas field in Sichuan Basin is faced with large remaining geological reserves and great development potential. However, the overall water production of the gas reservoir, the subsequent effective development of the gas reservoir is restricted, resulting in the current recovery degree of only 36.6 %. In order to maximize the remaining potential of the gas reservoir and improve the final recovery of the gas reservoir, Come up with the idea of "looking for gas with water and turning waste into treasure", systematically combs the natural gas and formation water components of Sinian gas reservoir, extract helium for natural gas components, extract precious metal ions from formation water, and comprehensively utilize heat energy, so as to realize the overall effective utilization of gas reservoir. The results show that: ① The helium content of natural gas in W gas field accounts for 0.2 %~0.35 %, which is 4~7 times of the helium industrial production limit （0.05 %）, and the helium reserve is about 0.8×10⁸ m³. The scale of helium resources is very considerable. helium resource scale is very considerable, and it is one of the large helium rich gas fields in China. ② The gas field water is rich in lithium, bromine and other trace element resources, in which the lithium content is 2~3 times the industrial exploitation value and the bromine content is 2~4 times that of the industrial exploitation value. ③ The temperature of gas field water can reach 90 ℃, and it is calculated as 5 000 m3/d, the annual available heat is 3.47×10¹¹ kJ, which can be saving 1.18×10⁴ t of standard coal. Through the analysis of comprehensive utilization examples of Sinian gas reservoir in W gas field, combined with the effective development and utilization of new energy, it provides a new idea for the enhanced oil recovery and potential analysis of other gas fields in the later stage of development.

The heat exchanger of medium-shallow borehole which have a deeper depth than the traditional ground source heat pump system and can sustain a notable load imbalance ratio and widen the application scope of geothermal energy. In order to investigate the long-term performance of medium-shallow borehole heat exchanger in the area with unbalanced cooling and heating load of buildings and the sustainable load imbalance ratio under different design parameters, a comprehensive numerical model is established based on the OpenGeoSys. The results show that the sustainable load imbalance ratio of medium-shallow borehole heat exchangers change with different scales. The load imbalance ratio of a single heat exchanger is 56 %, while the load imbalance ratio of the heat exchanger located at the edge of the array is the largest of 60 %, and the load imbalance ratio of the heat exchanger located in the center of the array is the smallest of 45 %. This indicates that the cold accumulation phenomenon will reduce the load imbalance ratio of the medium-shallow borehole heat exchanger. Therefore, in the actual operation process, the overall operation performance of the array can be avoided by shutting down some medium-shallow borehole heat exchanger located in the center of the array. Under three different arrangements, the load imbalance ratio of the medium-shallow borehole heat exchangers also changes, ranging from 53 % to 58 %. The average load imbalance ratio of the medium-shallow borehole heat exchangers in staggered arrangement is the highest, so it is recommended to adopt staggered arrangement in practical application. The results show that the newly proposed medium-shallow borehole heat exchanger can sustain a notable load imbalance ratio, and provide a basis for the design of medium-shallow borehole heat exchangers.

The stress field response of the geothermal reservoir induced by staged fracturing will have a direct impact on the wellbore integrity and casing deformation of the geothermal reservoir. Studying the stress field response of the geothermal reservoir induced by staged fracturing is important to guide the field fracturing. significance. At present, fracture mechanics is generally used to solve the stress field response induced by hydraulic fracturing. However, the stress field response of geothermal reservoirs induced by staged fracturing is essentially the problem of stress interference between fractures under the action of heat-fluid-solid coupling, which makes this problem difficult to solve. Fracture mechanics solutions are extremely complex. In view of this, the continuity assumption was introduced to transform this fracture mechanics problem into an elastic mechanics problem, and a single-connected analytical model of the stress field response of geothermal reservoirs induced by staged fracturing was established, which greatly reduced the difficulty of solving, and the stress field response after field fracturing can be analyzed more simply and effectively. Based on ABAQUS, a staged fracturing thermal-fluid-solid coupling numerical model for geothermal reservoirs was established, and the error of the analytical model was verified to be within 5 % by comparing the average stress in the x and y directions. Then, using the analytical model, the effects of cluster number, temperature difference and natural fractures on the stress field of geothermal reservoirs are discussed. The results show that as the number of clusters increases, the stress component in the x-direction increases and the stress component in the y-direction decreases in the geothermal reservoir; as the temperature difference increases, the stress components in the x and y directions in the geothermal reservoir increase accordingly; as the density of natural fractures increases, the stress component in the x-direction increases and the stress component in the y-direction decreases in the geothermal reservoir.

Fractured-cavity reservoirs have diverse storage spaces, strong heterogeneity, large differences in oil-water properties, high mobility ratio of immiscible nitrogen flooding in water flooding, serious water and gas channeling, limited sweeping range, and primary and secondary oil recovery stages. Oil recovery is much lower than that of clastic sandstone reservoirs. Taking the S91 fracture-cavity unit in Tahe Oilfield as the object, on the basis of geological modeling, history matching, remaining oil characterization and phase state experimental fitting, a numerical simulation study on enhanced oil recovery by hydrocarbon injection in fractured-cavity reservoirs is carried out, so as the evaluation of the hydrocarbon-gas miscibility conditions in fractured-cavity reservoirs, and the optimization of EOR parameters of hydrocarbon injection. The results show that the minimum miscibility pressure of injected hydrocarbon gas and formation crude oil in S91 unit is 42.5 MPa, which can be miscible under the current formation pressure. The mechanism of miscibility is vaporization gas flooding. As the content of heavy hydrocarbon components in the injected gas increases, the recovery factor increases. The gas injection method is gas injection in fractured reservoirs, and liquid recovery in caved reservoirs. The gas injection parameters are preferably 168×10⁴ m³, gas injection rate of 4×10⁴ m³/d, and injection-production ratio of 1∶0.9.

The thin sandstone reservoir in the delta front developed in the upper part of the K₁bs³ formation is an important area for the exploration of structural-lithological oil and gas reservoirs in the XH area. In recent years, Application of P-impedance and pre-stack deterministic inversion could not accurately predict the distribution of thin sandstone reservoirs in the target layer. In this paper, joint impedance and facies inversion（JI-FI） impedance and facies joint inversion technology is used. This technique uses pre-stack seismic gather data, and combines simultaneous inversion and Bayesian classification under the constraints of the P-wave, S-wave velocity and density depth trend of each lithofacies or fluid facies, the maximum expectation algorithm is used to iterate the impedance and facies, and the quantitative prediction of lithofacies/fluid facies and petrophysical properties （such as P-wave, shear wave impedance, density, V_p/V_s, etc.） in the target area is achieved. This method overcomes the uncertainty of inter-well P-impedance interpolation when conventional pre-stack inversion relies on wells to establish low-frequency models, especially under geological conditions with few wells and thin interbeds. The reservoir prediction results are in good agreement with the well, which provides a basis for lithological exploration and well location deployment in this area.

There’s large differences in oil bearing characteristics of Chang-8 reservoirs in different regions of southwestern Ordos Basin. The exploration potential is great. Studies on major control factors of oil accumulation and enrichment mode of Huanxi-Pengyang area have been carried out on the basis of fundamental oil formation condition analysis in southwestern margin of Ordos Basin to provide a theoretical support for the determination of oil exploratory potential and prediction of favorable zones. By the methods of formation test, logging and core analysis, organic geochemistry and thermodynamic simulations on the fluid inclusions, the migration and accumulation characteristics and major controlling factors of oil enrichment in Huanxi-Pengyang area is systematically analyzed based on the difference in sedimentary reservoir and reservoir characteristics of Chang-8 low-permeability tight reservoir. The results show that there is big difference exists in the features and formation conditions between north and south reservoir. As the source rock thickness is greater and hydrocarbon generation and expulsion conditions is better, and the overall physical property is good, it’s more favorable for oil charge and accumulation in Pengyang than that in Huanxi area. But structural adjustment influence secondary oil-gas migration or damage in southwestern margin contrast to basin center, resulting in more complex oil distribution. Thus, the oil-gas accumulation model of the Pengyang and Huanxi is further established while the former belongs to vertical hydrocarbon migration pattern and the latter lateral pattern. The research results provide significant guidance for next step of petroleum exploratory orientation evaluation and development for Chang-8 reservoirs in marginal areas of Ordos Basin.

Bubble point pressure（p_b） is an essential parameter for determining reservoir type, formulating reservoir development scheme and reservoir engineering calculation. It is also the basis for calculating oilfield reserves and selecting oil well working system. In order to conveniently and rapidly predict the bubble point pressure value of reservoir fluid, the empirical model for determining the bubble point pressure value of deep complex reservoir fluid is described based on a large number of PVT high-pressure physical property test data. And the main controlling factors affecting the bubble point pressure of oil in deep complex reservoir of Tarim oildom are analyzed and determined. Meanwhile, A model for rapid prediction of reservoir fluid bubble point pressure is established. Based on 132 groups of sample data in Tarim oil area, the regression analysis is carried out by using digital simulation software, and the values of 10 influencing factors and related parameters of the new bubble point pressure model are obtained. It is verified by the supplementary PVT experimental data of 10 subsequent formation fluid samples. Compared with the existing empirical formula, the prediction model has better prediction effect.

The Toutunhe Formation in Fukang Sag, Junggar Basin, is mainly characterized by low porosity and low permeability with many types of fillers and complex pore structures. But there is a serious contradiction between the potential acid sensitivity damage and the indoor evaluation, and the variability exists in the sensitivity of the reservoir. Therefore, the reservoir sensitivity evaluation and control factors are studied by the core experiments such as core displacement, casting thin section identification, nuclear magnetic resonance, scanning electron microscope, etc. The results show that in Toutunhe Formation, the velocity sensitivity is weak, the water sensitivity and salt sensitivity are both upper medium to strong, the alkali sensitivity is upper medium, and the acid sensitivity is weak to moderate weak. The difference of reservoir sensitivity is related to many types of interstitial fillers and complex pore structures. In the Toutunhe Formation reservoir enriched with the cement of authigenic quartz, whose diameter is less than 5 μm, the corrosion of the surface clay by the acid-base liquid lead to the exfoliation of the crystals such as the authigenic quartz. Then, these movable particles obstruct the pore throat. The mechanism of this kind of damage which shows a upper medium to strong acid sensitivity is different from that of the other traditional damage such as the secondary precipitation. The sensitivity damage mechanism shows that all kinds of sensitivities have superposition effects.

The application of multi-layer mining technology in reservoir is gradually extensive. Production splitting and stratification evaluation are regarded as important links, which affect the accuracy of dynamic reserve calculation and the reliability of development policy adjustment. However, the conventional formation coefficient（Kh） production splitting method still fails to fully consider the dynamic factors such as reservoir connectivity and pressure difference. Based on darcy formula and other seepage theory, a new production splitting method is put forward to clarify the role of the production of each layer in the development of reservoir. This method introduces the concept of “permeability contribution rate”, which is defined as the ratio of permeability of each layer to the sum of all permeability of high, middle and low layers, and comprehensively considers the relationship between permeability contribution rate, water content, and splitting coefficient, and proposes the production splitting of multi-layer mining with different permeability layers. Based on the research of eight groups of different permeability levels and polynomial regression calculation, the mathematical model for splitting of liquid production is established for different permeability layers considering water content, permeability range and other parameters. Through the comparison between the numerical simulation and the experimental test results, the splitting mode has small error and high accuracy, which can meet the needs of field application.