Horizontal Shale Gas Wells Research Articles

Research and engineering application of pre-stressed cementing technology for preventing micro-annulus caused by cyclic loading-unloading in deep shale gas horizontal wells

Shale gas exploration and development maintained good momentum, but it has some problems at the same time urgently need to be solved, such as sustained casing pressure (SCP), which brought a lot of safety issues and shortened the well service lifetime. A series of experimental investigations and numerical studies were carried out to analyze the development of the micro-annulus width of the second interface in the casing-cement sheath-formation assembly before and after using the pre-stressed cementing technology. Triaxial compression tests computed tomography scanning and accumulated plastic strain tests were conducted to evaluate the residual strain under the combined action of cyclic loading-unloading and confining pressure. Full-size cement sheath experiments were performed to quantify the width critical value of the micro-annulus when gas leakage began during multistage fracturing. The corresponding numerical models of the full-size cement sheath physical simulation facility and pre-stressed cementing technology of a real deep shale gas well were developed. Different combinations of factors were analyzed to quantify the variation of micro-annulus and tolerance ability of fracturing section numbers. The influence of a series of factors, including casing inner pressure, pre-stressed loading, and mechanical parameters of the cement sheath, were analyzed. The result of the research showed that the reduction of casing pressure and increase of pre-stressed loading could help to maintain the seal integrity of the cement sheath. Micro-annulus risks can be reduced through lowering elasticity modulus and raising Poisson's ratio. Eight deep horizontal shale gas wells were cemented with pre-stressed loading. The practical application results showed there was no SCP in prior and post-multi-stage fracturing, which proved the effectiveness of this method.

A new approach for gas-water flow simulation in multi-fractured horizontal wells of shale gas reservoirs

Shale gas reservoirs demonstrate low matrix porosity and permeability, and show obvious heterogeneity due to the existence of natural fractures. During the production process, fracturing fluid can easily invade the reservoir and result in a low fracturing flowback rate. The existing numerical methods are troublesome and have poor convergence. Therefore, it is necessary to develop a new approach to study the gas-water two-phase flow in shale gas reservoirs. In this paper, fractal theory is used to quantitatively characterize the heterogeneous fractures. A Mathematical model considering fractal induced-fracture distribution and gas-water two-phase flow in shale reservoirs is established. The meshless weighted least squares (MWLS) method is applied, for the first time, to the numerical simulation of gas-water two-phase flow in multi-fractured horizontal wells of shale gas reservoirs. Based on the moving least squares approximation, the variation principle is derived in detail. A numerical model of gas-water two-phase flow in the shale gas reservoir fracturing horizontal well based on the meshless method is obtained. The gas and water production of fractured horizontal shale gas wells are predicted by the model. The model simulation results are found to be in good consistent with the mathematical calculation results obtained through finite difference method. but the proposed new approach shows significant higher calculation efficiency. In addition, by applying this new approach, The influences of fracture distribution, initial water saturation, and reservoir reconstruction degree on the utilization range and production were also systematically compared and analyzed. The results showed that the smaller the fracture fractal index a in the reservoir reform area, the lower the pressure, the higher the daily gas production and the daily water production, indicating that the fracture network is densely distributed and the production effect is better. The larger the initial water saturation resulted in the greater flow resistance of the gas phase and the decrease of daily gas production. When the fracture spacing decreases in reservoir reconstruction, the daily gas production increases, but the increase range is gradually reduced and it has little effect on the daily water production.

“Unsteady intermittent coordination mechanism” of adsorbed gas desorption and transport in the late stage of shale gas development

The desorption of adsorbed gas and its diffusion in nano-channels are important mechanisms for the late stage of shale gas development. However, there is no commonly accepted theory to reveal the laws of these mechanisms in sustaining appreciable shale gas production after relatively high flow period. Experimental simulation of shale gas production and its sound theoretical deduction are capable of providing useful in-situ development guidance. In this paper, experiments are carried out to simulate the depletion production performance of horizontal shale gas wells and to explore the production laws and scientific explanations. By establishing the resemblance between the physical experiment and the in-situ development, the high matching of experimental results and real production data is realized, making the reliable prediction of gas production performance happen. It is found by the experimental results that the production of shale gas wells in the middle and late stages is dominated by a special gradual release mechanism, which is named “unsteady intermittent coordination mechanism” in this work. This special mechanism is mainly restricted by the gas mobility in shale nanopores and the supply and transport capacity in the pore-fracture system. In view of adsorption/desorption, the late-stage production characteristics are largely dependent on the adsorption and desorption processes, and the unsteady mechanism of adsorbed gas desorption is preliminarily revealed from the microscopic viewpoints of desorption laws at different pressures and in different pores. Interestingly, the desorption itself is predicted to be unsteady in essence. In terms of mobility, the transport of desorbed gas in single channels and pore networks undergoes a slow cycle of molecular accumulation and release due to the presence of wall confinement in the microscopic pores. After flowing into the fracture system, the gas will be quickly diverted to the production well. Meanwhile, the fracture system cannot be supplemented in time by gas in the micro-nano pores. To sum up, a qualitative understanding and scientific explanation of the “unsteady intermittent coordination mechanism” of the adsorbed gas desorption and transport in the late stage of shale gas development are realized.

Effect analysis of borehole microseismic monitoring technology on shale gas fracturing in western Hubei

Hydraulic fracturing technology is an important means of shale gas development, and microseismic monitoring is the key technology of fracturing effect evaluation. In this study, hydraulic fracturing and microseismic monitoring were simultaneously conducted in the Eyangye 2HF well (hereinafter referred to as EYY2HF well). The target stratum of this well is the second member of the Doushantuo Formation of the Sinian System, which is the oldest stratum of horizontal shale gas wells in the world. A total of 4341 microseismic fracturing events were identified, and 23 fracturing stages of the well were defined. The fluctuation of the number of events showed a repeating “high-low” pattern, and the average energy of these events showed minimal differences. These findings indicate that the water pressure required for the reconstruction of the EYY2HF well is appropriate. The main body of the fracture network extended from northwest to southeast, consistent with the interpretation of regional geological and seismic data. The stimulated rock volumes showed a linear increase with the increase of the fracturing stage. Some technological measures, such as quick lift displacement, quick lift sand ratio, and pump stop for secondary sand addition, were adopted during fracturing to increase the complexity of the fracture network. Microseismic fracture monitoring of the well achieved expected effects and guided real-time fracturing operations and fracturing effect evaluation.

Integrity tests of cement sheath for shale gas wells under strong alternating thermal loads

During large-scale hydraulic fracturing in shale gas horizontal wells, a cement sheath easily loses its integrity due to the fluctuation and continuous change of wellbore temperature and pressure and the cyclic loading and unloading, which will threaten wellbore integrity. In order to figure out the failure mechanism of cement sheath integrity under strong alternating thermal loads and prevent the failure of cement sheath barriers during large-scale hydraulic fracturing in shale gas horizontal wells, this paper adopted the independently developed experimental device to test and evaluate the sealing integrity and mechanical integrity of the full-scale combination of production casing, cement sheath and intermediate casing under strong alternating thermal loads. And the integrity experimental results of two kinds of full-scale cement sheaths (conventional and high-strength cement sheaths) under three kinds of strong alternating thermal loads (cycle number for the occurrence of discontinuous CO2 bubble: 4 and 14; cycle number for the occurrence of continuous CO2 bubble: 5 and 15; alternating thermal load: 30–120 °C and 30–150 °C) were obtained. And the following research results were obtained. First, alternating thermal load has a significant negative impact on the integrity of cement sheath, and with the increase of alternating temperature and temperature difference, the thermal cycle number characterizing the sealing integrity of cement sheath reduces sharply. Second, the interfacial mechanical property indicators that characterize the shearing force between cement sheath and casing and the axial and radial bonding strength decrease with the increase of the alternating temperature. Third, the micro annulus in cement sheath is mainly caused by discordant deformation between the casing and the cement sheath materials, and the mechanical degradation and deterioration of the set cement induced by the alternating thermal load aggravate the failure of the sealing integrity of cement sheath to a certain degree. In conclusion, the research results can provide a reference for the design of large-scale fracturing in deep shale gas horizontal wells.

Productivity forecast for multi-stage fracturing in shale gas wells based on a random forest algorithm

ABSTRACT This study addresses the problem of low-accuracy production forecasting for horizontal shale gas wells by applying a random forest algorithm and considering both the physical reservoir parameters and the engineering fracturing parameters. Based on the interpretation of logging data, drilling data, fracturing data, and sectional production data from the Fuling shale gas field, the random forest algorithm was used to build a regression model, through partial correlation analysis and recursive feature elimination to select the optimal key influencing factors. The study revealed that the layer, cluster spacing, number of clusters, 40/70 mesh low-density ceramsite (medium sand), and total proppant are the key factors influencing sectional production, and they all have different effects on it. The random forest algorithm showed better prediction capacity than the other algorithms. Its coefficient of determination and root-mean-square error on the test set were 0.723 and 0.319, respectively, which indicates that it is an effective approach and has good generalization ability. The prediction results of the productivity regression model based on the random forest algorithm, combined with the trend surface response analysis, were used to obtain the optimal values of the six key fracturing parameters of the unfractured well.

Influence of natural fractures on fracturing of horizontal shale gas wells and process adjustment

Influence of natural fractures on fracturing of horizontal shale gas wells and process adjustment

Trajectory Optimization of Deep Shale Gas Horizontal Wells

The development mode of deep shale gas “Pad drilling” cluster horizontal wells could greatly reduce the single-well drilling cost and is also the significant measure for scale benefit development of shale gas. For pad drilling, the small wellhead distance of cluster well group, complicated well profile and long horizontal section result in such engineering problems as high well collision probability in upper well section, high trajectory control difficulties and large drill string torque and drag. A reasonable 3D horizontal well profile and the reasonable profile parameters are the premise for the safe and rapid drilling of shale gas horizontal well. Therefore, optimizing type and the well profile parameters suitable for deep shale gas horizontal well could help improve drilling efficiency, lower drilling risk and save drilling cost. In this paper, the three types of trajectory profile, including 3D trajectory in spatial oblique plane (large 3D), dual 2D trajectory and dual 2D and small 3D combined trajectory profile were developed, and under the same surface location and target zone, three different types of shale gas horizontal well were planed; the differences of these three trajectories in well depth, drill string torque and drag and well separation factor were compared through drill string torque and drag analysis and collision prevention analysis. The analysis results show: Dual 2D trajectory or dual 2D and small 3D combined trajectory is featured by small drill string drag and torque, low trajectory control difficulty and low well collision probability and is therefore more suitable for trajectory plan of deep shale gas horizontal wells.

A New Wellbore Stability Model for Shale Gas Horizontal Wells with Effects of Bedding Planes and Water Content

Shale gas exploration and development have become a hot spot in the natural gas industry. Providing wellbore stability is one of the major engineering problems occurring in the process of drilling of horizontal shale gas wells. In this paper, based on circumferential stress analysis of horizontal wells and analysis of the geometrical relationship of bedding planes and the wellbore, a new horizontal wellbore stability model is introduced. The proposed model takes into account the effect of bedding planes and water content on the strength parameters of shale. Based on actual field data of a shale gas well, the proposed model is compared with the wellbore stability model for an intrinsic rock formation. The results show that the existence of bedding planes affects the stability of a wellbore, making it less stable. Meanwhile, the maximum and minimum values of collapse pressure density for different azimuths of wellbore increase linearly with increase in water content. Moreover, the results also show that factors of the wellbore azimuths and the bedding planes dip angle and dip direction have a significant impact on the wellbore stability of horizontal shale gas wells.

Study on Horizontal Well Over-replacement Fracturing

Over-displacement technology often occurs in the fracturing process of horizontal gas wells. The effect of horizontal shale gas wells productivity with different fracture morphology considering over-displacement were analyzed by numerical simulation. The results show that the over-displacement productivity is only 12.3%-15.0% of the equilibrium displacement productivity considering the complete fracture closure, and the fracture morphology has no effect on the productivity. Therefore, the amount of over-displacement hydrofrac fluid should be minimized in horizontal gas well, the fracturing fluid can rapidly gel-break and flowback after fracturing, proppant can flow back or settle at the fracture seam, and complex fractures can be formed near the wellbore as far as possible, so that it can reduce the impact of over-displacement on productivity. This study can provide a theoretical basis for fracturing design and productivity prediction of horizontal gas wells.

Effect of the hydraulic fracturing-induced slippage of regional natural fracture on casing deformation in horizontal shale gas wells: A case study on the Weiyuan block

Casing deformation problems are widespread in the shale gas field, and the dominant natural fracture reactivation and slippage are treated as the main reasons for these casing deformations. This study establishes a mechanical model and uses the field data of Weiyuan to study the fracture slippage and the casing deformation. According to rock mechanics, the dominant natural fracture can be reactivated by the fluid injected into the fracture. A higher fluid pressure in the fracture can induce a larger slippage and a higher shear stress on the casing. The fracture slippage is not uniform along the fracture. Moreover, the maximum slippage is located at the center of the reactivation zone. The in-situ stress, friction coefficient, and angle between the fracture and the maximum in-situ stress can affect the slippage. Case studies on the casing deformation of two wells in Weiyuan have shown that the calculated slippage according to the analytical model herein is in accordance with the detected data in the field. In summary, this study provides a reliable and quick method for determining the slippage of the dominant fracture reactivation based on the distance from the fracture center.

Mechanism and numerical simulation of a new device of bypass cementing device for controlling casing shear deformation induced by fault slipping

Casing shear deformation has been a serious issue to be resolved during multistage fracturing in shale gas horizontal wells in the world, which significantly increased the well stimulation cost and reduced the production capacity. Fault slipping was identified as a significant cause and not easy to control. A new device of bypass cementing device, along with the indispensable accessories, was proposed and designed. The local pressure loss of the device was calculated to analyze the compatibility of geometric dimensions between the wellbore and device, and the device structure parameters of the tools were optimized. A matched application process that was able to make the slurry bypassing nature fractures developed zone was established. Then a series of corresponding numerical models of the device were developed and to simulate the variation of inner diameter in the casing deformed part using the shell-to-solid coupling method, and the shear deformation degrees before and after using the new device were compared. Simulation results showed that after using the bypass cementing device, the reduction of casing inner diameter after fault slipping was reduced by about 63.75%–75.6%, which could effectively protect the casing integrity. The method in this study supplied an important solution for dealing with the problem of casing shear deformation caused by fault slipping induced by multistage fracturing in shale gas horizontal wells.

Mechanism of migration and settlement for temporary plugging ball in shale gas horizontal wells

In order to determine the migration and settlement mechanism of temporary plugging balls in horizontal wells, the rules for distribution, migration and settlement of balls in different location were researched through calculation, coupling fracturing fluid and characteristics of movement based on CFD (computational fluid dynamics), DEM (discrete element method) and DDPM (dense discrete phase model), and the intensity, plane and spatial distribution of the microseismic events before and after ball-addition were analysed. The results showed that: First, the central flow core in the pipeline is the main migration carrier of the temporary plugging balls and proppants, low-viscosity liquid performs differences when inflowing at various perforation holes. The settlement and plugging in downstream cannot be effectively improved while the upstream without balls’ settlement. Second, due to the fluid resistance, the mean velocity of temporary plugging balls decreases and balls spread along the casing wall while the interaction force can be ignored. Under different displacement, the temporary plugging balls’ migration speed has a relatively stable value, the displacement of 5 m3/min is the critical value for the effective setting of temporary plugging balls. Thus, most of the micro-seismic events after ball-addition were concentrated in the upstream clusters, the impact scope of the micro-seismic events of 6-clusters is greater than that of 8-clusters perforation. After ball-addition in 6-clusters, the key effect is to improve the complexity of the microfracture network, while in 8-clusters to improve SRV (simulated reservoir volume) for the beginning first 4 clusters. So that is, increasing the number of clusters will lead to an inadequate microfracture length extension and only SRV (simulated reservoir volume) near the wellbore zone was improved.

Study on mechanical properties and wellbore stability of deep brittle shale

As the drilling depth of shale's oil and gas wells increases worldwide, the problem of borehole collapse and instability becomes increasingly serious. Due to the high content of brittle minerals in deep shale, the complex situation of an underground collapse of a site is often manifested as borehole wall caving and falling. On the basis of the deep shale of China's Longmaxi formation, we developed a simulation experiment involving the complex loading mechanics of underground working conditions. The influence of loading and unloading confining pressure speeds and the sealing properties of drilling fluid on the mechanical properties of rock were analyzed. We established the dynamic changes in borehole formation, combining seepage and pore pressure, the effective stress field around the well, and a method of evaluating wellbore stability in deep shale gas horizontal wells. The results show that the deep shale of the Longmaxi formation has a high brittle mineral content and is prone to brittle fracturing along parallel bedding surfaces under downhole pressure. The effective liquid column pressure at the bottom of the wells change noticeably under different working conditions. Changes in bottom hole fluid column pressure are the cause of the complicated situation of well leakage and overflow in the horizontal sections of the Longmaxi formation. The effective support confining pressure of borehole wall rock differs with different tripping out speeds. The faster the tripping out is, the less the support confining pressure of the wellbore rock and the easier it is to induce the rock to break down along the bedding. The effective sealing property of drilling fluid also affects wellbore stability. A good sealing property of drilling fluid can improve the supporting effect of the fluid on borehole wall rock and improve its resistance strength. On the whole, the pressure of the bottom hole liquid column is effectively controlled during drilling in the Longmaxi formation; this can avoid complicated situations such as well leakage. The results of this study provide a theoretical basis for the study of wellbore stability in deep shale formations during the drilling process.

Research on temporary plugging refracturing technology for shale gas wells

According to the variation law of stress induced by hydraulic fractures during the initial fracturing of shale gas wells, the temporary plugging refracturing technology was studied. Based on the research on the mechanism of fracture reorientation from temporary plugging, the process parameters (such as the particle size combination of the temporary plugging agent, the temporary plugging timing, and the amount of temporary plugging agent) were optimized, and the key material for temporary plugging were evaluated. Temporary plugging refracturing technology suitable for shale gas horizontal well was initially formed. Excellent results of trial test were achieved and the production rate after refracturing was increased by 5 times compared with that before stimulation. This study can provide some reference for temporary plugging refracturing of shale gas wells.

Wellbore cleaning technologies for shale-gas horizontal wells: Difficulties and countermeasures

The application of horizontal well drilling and large-scale sand fracturing can secure an increased production in shale gas reservoirs despite of frequent gas wellbore blockage. It is vital to remove the residual bridge plug debris and sand in wellbore cleaning operation and to ensure an unblocked downhole production channel of shale gas well for a safe and smooth production process. In this paper, the current situations of the wellbore cleaning technology for horizontal wells were analyzed, and the technical challenges in wellbore cleaning treatment of shale gas horizontal wells were summarized. Based on global development of wellbore cleaning technologies for horizontal wells, technical researches were carried out on cleaning tools & technologies and working fluid performance, and cleaning treatment tools were studied and developed. Besides, technical measures of cleaning treatment were put forward and their field application effects were analyzed. Results reveal that the milling–fishing integrated tool, developed to treat large bore bridge plug, is capable of washing-over and fishing out large bore bridge plug in one trip after running in the hole; for long horizontal sections where reverse cyclone sand-washing tool is applied, the tool can prevent sand from settling so as to flush sand out of the wellbore; for normal-pressure and high-pressure wells, gas well backflow fluid, KCl and CaCl2 solution may serve as working fluid, while for low pressure wells, foam fluid can be used; for low-pressure wells, the negative pressure fishing tool is designed and optimized to drive debris or sediment into the tool through forming local negative pressure adsorption, thus complete the fishing operation. In conclusion, the new wellbore cleaning technology, which suits shale-gas horizontal wells, has laid the groundwork for large-scale wellbore cleaning treatment of shale gas wells.

Numerical simulation of recovered water flow and contaminants diffusion in the wellbore of shale gas horizontal wells

On the basis of momentum conservation and mass conservation theory, this paper proposes mathematical model to investigate recovered water flow and contaminant diffusion in the wellbore of shale gas horizontal wells. Two significant improvements are made to conventional models. One is that the quality and velocity flow of each cluster are considered as dynamic parameters in equation of flow, and another one is that source terms and reaction terms are considered as dynamic parameters in equation of contaminant diffusion. The validity of the model of recovered water flow and contaminants diffusion is verified by comparing the predicted results with the actual production data and the experimental data in the literature. Then main factors affecting the concentration of contaminants in horizontal wells are studied systematically. It can be shown that the concentration of contaminants at wellhead increases linearly with the linear increase of the initial concentration, boundary concentration and the source term in the whole time period. The concentration of contaminants increases nonlinearly with the linear increase of the length of horizontal wellbore and flow-back average velocity of recovered water in different time periods. The research of this paper provides guidance for the control of recovered water.

Effect of Natural Fractures on Shale Gas Reservoir Reconstruction

Natural fractures have great influence on shale gas reservoir reconstruction. In order to find out the law of influence, comprehensive analysis of the characteristics of geological natural fracture and fracturing fracture before fracturing is carried out. Firstly, natural cracks are identified by using coherence and maximum relief attributes of ground seismic data. Secondly, the characteristics of hydraulic fracturing cracks and the response characteristics of natural cracks are analyzed by using the results of microseismic monitoring and positioning and the data of hydraulic fracturing construction. Finally, the influence of natural fracture on the effect of fracturing reconstruction is summarized. The results show that the response characteristics of natural cracks predicted by surface earthquakes are different in the results of microseismic monitoring. According to the response characteristics of natural cracks, they can be divided into active and inactive natural cracks. Combining with the fracturing data, it is found that both active and inactive natural cracks will affect the fracturing construction to varying degrees. Active natural fractures are prone to abnormal construction conditions such as sand plugging, casing deformation and fracturing fluid leakage. Non-active natural fractures play a role of stress shielding under certain conditions, which can affect the fracturing fracture morphology and the effect of fracturing reservoir reconstruction. The research results provide a basis for shale gas horizontal well trajectory optimization and adjustment of hydraulic pressure construction parameters.

Fracturing technologies of deep shale gas horizontal wells in the Weirong Block, southern Sichuan Basin

Stimulation of hydraulic fracturing of horizontal shale gas wells in Weirong Block has always been facing many difficulties due to many factors such as complicated geological conditions, small differences between the horizontal principal stress and the vertical principal stress, high working pump pressures, and low sensitive sand ratios. In view of this, by combing the geological structure, engineering geological characteristics and the difficulties of fracturing of deep shale gas wells in Weirong Block, learning from the general idea of volumetric fracturing for shale gas reservoirs at home and abroad, we determined the main ideas and technical countermeasures for fracturing in the area and applied them to the subsequent fracturing practices of shale gas wells. And the following achievements were obtained. First, the conventional fracturing technology applied to the shale gas wells in Weirong Block resulted in low fracture complexity, small stimulated reservoir volume (SRV), difficulties in guaranteeing the effectiveness of perforation clusters, low strength of proppant adding, difficulties in obtaining higher conductivity, poor stable production capacity after stimulation, and difficulties in meeting the need of well fracturing with casing deformation. Second, in view of the difficulties of fracturing stimulation in deep shale gas wells of Weirong Block, super high pressure, huge displacement, large fluid volume, temporary plugging and diverting in fracturing, and variable displacement technology can effectively increase SRV and the complexity of fractures in distant wells. The effectiveness of multi-cluster perforation can be guaranteed by comprehensive utilization of multi-cluster perforation optimization technology, big displacement technology and temporary plugging and diverting & fracturing technology at slots. The continuous proppant-adding technology with huge displacement, high viscosity, low sand ratio, low density and small particle size can improve sand adding strength and fracture conductivity. Besides, the stimulation technology for casing deformed wells using coiled tubing fast processing + small diameter bridge plug and separate pumping technology of perforating gun have been formed. Third, after the above fracturing technologies have been applied in five shale gas horizontal wells in Weirong Block, the average absolute open flow (QAOF) reached 26.11 × 104 m3/d, indicating a good stimulation effect. In conclusion, this paper can provide meaningful reference for the development of deep shale gas wells of the similar type.

Application of Point-by-Point Vector Synthesis in Walkaway VSP Logging Data Processing

At present, it is necessary to use Walkaway VSP logging imaging data to drill horizontal shale gas wells in exploration areas lacking three-dimensional seismic data. Walkaway VSP logging imaging profile can delineate the formation structure around wells, obtain detailed information of dip, inclination and fault around wells, and guide the trajectory design of horizontal wells. But VSP logging is richer and more complex than conventional seismic data. The precondition of up-going wave imaging is to separate up-going P-wave or converted S-wave from complex wave field. Nowadays, most vector synthesis techniques can not completely separate up-going P-wave from up-going converted wave, which affects the accuracy of final imaging results. In order to achieve the best wave field separation effect of VSP logging data, the point-by-point vector synthesis technique is adopted. Firstly, the directional rotation synthesis of horizontal components is carried out according to the maximum energy criterion. Then the rotational synthesis of horizontal and vertical components uses ray tracing based on velocity model to estimate the polarization angle of time-varying upward reflected P-wave or converted wave. The method of “velocity fine-tuning scanning” is applied to search for the best synthesis angle, and the point-by-point vector synthesis is carried out by calculating the time-varying polarization angle. Finally, the best separation effect data are selected as the final vector synthesis result. This technique solves the problem that conventional vector synthesis cannot completely separate up-going P-wave from up-going converted S-wave. Upward P-waves acquired after separation has clear characteristics, more continuous phase axis and good fidelity processing effect, which lays a solid foundation for fine imaging of target formation in the study area and has become an indispensable key supporting technology for optimizing the trajectory of horizontal wells in shale gas development in Sichuan Basin.