Table of Content

10 August 2024, Volume 46 Issue 4

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A Special Issue of Exploration & Development Technologies for Deep and Ultra Deep Oil and Gas Reservoirs

Hydrocarbon Accumulation Process and Multiphase Formation in the F$_{\rm{{Ⅱ}}}$21 Strike-slip Fault Zone of Tazhong Uplift

XIONG Chang, ZHAO Xingxing, WU Jiangyong, ZHANG Xinqiao, WANG Peng

2024, 46(4):  1-18.  DOI: 10.11885/j.issn.1674-5086.2024.02.29.06

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Aiming at the complicated phase distribution of Ordovician reservoirs in Fault F$_{\rm{{Ⅱ}}}$21 of Tazhong Uplift, we make a comprehensive analysis of tectonic analytical geochemistry, and find out that the plane distribution of oil and gas physical properties such as oil density, gas drying coefficient, gas oil ratio, etc. is closely related to strike-slip fault segment structure, that condensate gas reservoir develops in the north of the wing tail structure zone, and that volatile oil reservoir and crude oil reservoir develop successively in the south area. The crude oil in the F$_{\rm{{Ⅱ}}}$21 fault is the same as that of the northern depression Fuman and Shunbei areas, mainly from Lower Cambrian source rocks. The maturity of crude oil decreases from north to south along the fault zone. Natural gas in the north of the fault zone is mainly crude oil cracking gas, and in the central and southern parts mainly kerogen cracking gas. The Ordovician reservoir in the F$_{\rm{{Ⅱ}}}$21 fault zone underwent multi-stage oil and gas injection, and the wing tail graben site was a favorable filling point for oil and gas, and the strong charging and transformation of pre-salt crude oil cracking gas in the Himalayan period was an important reason for the formation of condensate gas reservoir in the northern part of the fault zone. Affected by the paleostructural, the oil resources generated in the Late Caledonian and Late Hercynian periods were mainly accumulated in the southern nose uplift area of the wing tail graben structure.

Differential Characteristics and Evolution of Conjugate Strike Slip Faults in the Halahatang Area, Northern Tarim Basin

CHEN Lixin, WANG Shenglei, WAN Xiaoguo, SU Zhou, MA Bingshan

2024, 46(4):  19-37.  DOI: 10.11885/j.issn.1674-5086.2023.11.17.01

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Non-classical X-type conjugate strike-slip faults are observed in the Halahatang Oilfield, which have obvious differences in zoning, stratification, segmentation and evolution characteristics, constraining oil and gas exploration and exploitation. Based on the 3 400 km$^2$ seismic data, this paper describes the stratification and segmentation characteristics of two strike-slip faults in NE direction and NW direction, and analyzes the differential evolution characteristics and mechanism. The results show that 1) from north to south, fault maturity and extensibility become weaker, and stress perturbation by NE-striking faults increased; from deep to shallow layers, the disturbance effect of NW-trending faults on NE-trending faults became weaker; deformation degree and maturity decreases upward in NW-striking faults, but increases in NE-striking faults. 2) Strike-slip fault underwent multiple evolution stages in Halahatang Area, which can be divided into Middle Ordovician conjugate fault formation stage, Carboniferous-Permian transtensional strike-slip fault reactivation stage, and Meso-Cenozoic transtensional strike-slip fault reactivation stage. The NE- and NW-striking faults had differential fault evolution process. 3) Mechanism of fault formation and reactivation changes during the evolution process. The strike-slip fault system during the Middle Ordovician is controlled by the superimposed deformation of pure shear and simple shear, and were also controlled by stress field, pre-existing structure and regional strata thickness. The reduction of stress from north to south and the change of associated stress field resultes in the difference of fault styles in the south and north.

Optimization of Pseudo Elastic Wave Reverse Time Migration with Logging Correction in TTI Media

ZENG Qingcai, WANG Qinghua, ZENG Tongsheng, CHEN Sheng, ZHANG Kai

2024, 46(4):  38-50.  DOI: 10.11885/j.issn.1674-5086.2024.04.17.03

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In anisotropic media, seismic waves have different velocities in different propagation directions. The use of isotropic wave equations cannot accurately describe the propagation of seismic waves, which can lead to inaccurate positioning of deep events during imaging. On the basis of the TTI medium elastic wave equation, this paper sets the shear wave velocity to a smaller value and introduces a source loop to eliminate pseudo shear wave artifacts. On the other hand, logging data is used to constrain and correct the parameters field, in order to improve the imaging accuracy of deep and complex structures. The reverse time migration(RTM) method can have an impact on imaging due to low-frequency noise. Therefore, based on the Laplacian filtering operator for denoising, the paper extracts the angle domain common imaging point gathers(ADCIGs) and uses angle-selected stacking imaging to suppress strong amplitude low-frequency noise caused by inaccurate migration parameters. The real data requires a large amount of computation during imaging. In this article, the CPU/GPU cooperative operations are used to accelerate migration and improve computational efficiency. The model and real data results show that the TTI-RTM method based on logging data constraints can accurately image deep and complex structural target areas, which also proves the feasibility of the method.

Characterization and Effectiveness Evaluation of Deep Reservoir Fractures Under Oil-based Mud

YANG Fenglai, CHEN Rong, ZHOU Qing, WANG Jun, DAI Li

2024, 46(4):  51-64.  DOI: 10.11885/j.issn.1674-5086.2024.04.30.01

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The Kuqa Area is a typical fractured tight sandstone reservoir with dense lithology and low porosity. Validity of fractures is a key factor in the formation of a good reservoir. Therefore, how to accurately identify fractures and evaluate their effectiveness is the primary problem in oilfield exploration and development. Due to the needs of drilling engineering, most wells in the Kuqa Area are drilled with oil-based mud. The electrical conductivity of oil-based mud is poor, and it is difficult to effectively identify fractures with early oil-based mud electrical imaging logging tools due their low resolution. Therefore, the combination of oil-based mud electrical imaging logging tools (EI) and ultrasonic imaging tools (UXPL) can be used to extract structures and pick up fractures with different opening degrees, effectively solving the problem of fine identification of bedding and fractures. This article also introduces the method of using non-conductive mud geological imaging (NGI) to identify fractures, and systematically analyzes the relationship between normal stress on the fracture surface, the angle between fracture direction and maximum principal stress, and production capacity. A quantitative standard for evaluating the effectiveness of oil-based mud fractures in the Kuqa Area is established. In practical applications, this set of crack fine identification of fracture and effectiveness evaluation methods effectively guides production operation measures and provides technical means for the evaluation and development of fractured tight oil and gas reservoirs.

Technology for Precise Positioning of Ultra-deep Fracture-porous Carbonate Reservoirs

LI Guohui, GUO Yue, SUN Jiaqing, DING Yao

2024, 46(4):  65-73.  DOI: 10.11885/j.issn.1674-5086.2024.04.16.02

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The fracture-porous carbonate reservoirs in the Tarim Basin is deeply buried, and have small storage spaces and strong heterogeneity, bringing difficulties to accurate location of reservoirs and precise positioning of reservoir spaces. This poses great challenges for well-targeting and optimizing drilling trajectories, and limits well deployment and rapid production. To address these challenges, a study on precise reservoir positioning driven by VSP (Vertical Seismic Profile) was conducted using pre-stacked seismic data such as gathers and velocity fields, as well as VSP data collected during drilling operations. By optimizing the processing work-flow, the timeliness of delivering results within 72 hours was ensured, and precise positioning of the reservoir was achieved without affecting the drilling speed. This method has been successfully applied in the real-time tracking of more than 120 wells, resulting in an improvement in the direct drilling encounter rate of the reservoirs from 60$\%$ to 80$\%$, and increasing in the success rate of drilling to over 90$\%$. It provides valuable insights for reservoir prediction and precise positioning in similar fracture-porous reservoirs.

Construction of Injection and Production Well Pattern for Fault-controlled Fractured-vuggy Carbonate Vertical Plate-shaped Reservoirs

DENG Xingliang, ZHANG Shifan, WANG Peng, WANG Peng, ZHANG Jie

2024, 46(4):  74-84.  DOI: 10.11885/j.issn.1674-5086.2024.01.29.02

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The fracture-vuggy structure and connection relationship of fault-controlled fracture-vuggy carbonate reservoirs are complex, and traditional well pattern deployment is prone to produce low-productivity wells. A three-dimensional injection and production well pattern needs to be constructed to increase productivity. The influence of different factors on the sweep coefficient of the three-dimensional injection and production well pattern in the Manshen 3 and Manshen 4 well areas of the Tarim Fuman Oilfield was studied through reservoir numerical simulation, and a pilot test plan was designed to predict productivity. The results show that the sweep coefficient is the largest when the gas injection wells and production wells are arranged in a single staggered manner in the Manshen 3 well area; the greater the depth of the production wells, the greater the sweep coefficient; the sweep coefficient is stable within the range of 500$\sim$1 000 m between injection and production wells, and decreases significantly when the distance increases to 1 500 m. The sweep coefficient is the largest when gas injection wells, water injection wells and production wells are arranged in a single staggered manner in the Manshen 4 well area. In the pilot test, the plans of ``N$_2$ injection in the shallow part and production in the deep part" and ``N$_2$ injection in the top part, water injection in the bottom part, and production in the middle part" are adopted in the Manshen 3 and Manshen 4 well areas respectively. The recovery rates at the end of the stage reach 21.3% and 22.4% respectively, which is a significant improvement compared to the basic depletion development and water injection development plans.

Numerical Calculation of Multi-field Damage Coupling Fracture Initiation Pressure for Ultra-deep and Extra-deep Carbonate Reservoirs

GUO Jianchun, GUAN Chencheng, REN Jichuan, GOU Bo, ZENG Ji

2024, 46(4):  85-96.  DOI: 10.11885/j.issn.1674-5086.2024.06.06.01

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Ultra-deep carbonate reservoirs are characterized with high initiation pressure, leading to difficulties in fractures initiating. Acid can react with the reservoir matrix, enhancing porosity, increasing permeability, and deteriorating the mechanical properties of the rock, thereby reducing the initiation pressure. However, there lacks accurate calculation methods of fracture initiation pressure for acid-damaged carbonate reservoirs, making it challenging to design initiation pressure reduction measures. This study tested the dynamic Young$'$s modulus of cores after drilling fluid immersion and acid displacement, establishing a damage evolution equation for carbonate rocks under different fluid disturbance states. In addition, a numerical calculation model was established to couple flow, chemical, and stress-damage fields during acid fracturing to estimate the fracture initiation pressure. The results indicate that when both drilling fluid and acid fluid are affected, for reservoirs with a porosity below 4.32% and an acidizing time less than 4.08 minutes, the damage factor is below 0, which means that it is unable to mitigate the increase in Young's modulus caused by drilling fluid. During the operation of ``acid displacement of wellbore + acid immersion damage+ acid fracturing", the 8 833 m section of Well P1 reached the fracture initiation condition at the 73rd minute with the damage factor of 0.301 and fracture initiation pressure decrease of 29 MPa; as a result, this well was opened successfully. The calculation deviation of the model ranged from 1% to 5%, resulting in an improved accuracy of 3 to 10 percentage points when compared to traditional analytical models, this indicates that the model is particularly valuable for the calculation of fracture initiation pressure and designing acid damage measures in the Dengying Formation, as well as in similar carbonate reservoirs.

A Radial Unsteady Water Invasion Model for Ultra-deep Multi-porosity Reservoirs

XIAN Bo, ZHU Songbai, ZHOU Jie, FAN Qiuhai, NIE Yanbo

2024, 46(4):  97-106.  DOI: 10.11885/j.issn.1674-5086.2024.02.01.02

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In order to further understand the water invasion law of ultra-deep multi-porosity reservoir, the radial unsteady water invasion model for ultra-deep multi-porosity reservoirs was established in dual-porosity reservoirs and tri-porosity reservoirs by assuming that the aquifer was infinite or closed. Mathematical methods such as Laplace transform were used to solve the model, and the cumulative water invasion solution in Laplace space was obtained. Then the cumulative water invasion solution in real space was obtained through numerical inversion. The water invasion curves of infinite aquifer and closed aquifer in multi-porosity reservoirs were programmed and their differences were compared. Then the parameter sensitivity of the water invasion curves in multi-porosity reservoir was analyzed. Finally, the model was verified and analyzed by using the field data of ultra-deep fractured-vuggy reservoir in Tarim Basin combined with the principle of material balance. The results show that the water invasion curve of the infinite aquifer keeps rising, and the water invasion curve of the closed aquifer keeps stable in the later stage and there is a“water invasion step”. Water radius and storativity ratio mainly affect the position of water invasion curve. The inter-porosity flow coefficient mainly affects the time of“water invasion step”. The water invasion model can accurately calculate the amount of cumulative water invasion. The water invasion model established and the water invasion curves drawn can provide theoretical reference for the study of water invasion mechanism in ultra-deep multi-porosity reservoirs.

Heat Transfer Model of Deep Reservoir and Calculation of Oil Column Height

LIU Yong, YUAN Xiaoman, LU Zhongyuan, YE Sijie, LI Xiaolong

2024, 46(4):  107-114.  DOI: 10.11885/j.issn.1674-5086.2024.02.21.03

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Deep oil reservoir is characteristic of deep buried depth and large thickness, and is hard to drill through the oil formation. To address the issue of oil column height calculation for deep oil reservoirs, we established a heat transfer model of deep reservoir by considering the vertical heat transfer process from the oil-water interface to the wellbore after well production. We solved the model using variable substitution, variable separation and Fourier transform, and then derived the calculation formula of oil column height. By only using the temperature data at the bottom hole before and after well production, we can calculate oil column height. A pilot test was carried out at an oil well of a deep reservoir located at Tarim Basin to demonstrate the calculation process of oil column height. At the same time, by substituting the testing well data into the heat transfer model, we simulated the values of formation temperature and temperature gradient at different location of the oil formation at different production time. Then, we plotted the temperature distribution curve for different production time and the dynamic temperature curve for different formation location. The simulation results showed that formation temperature distribution took on nonlinear dynamic variation characteristics. The established heat transfer model is a good tool to calculate oil column height for deep oil reservoirs.

Typical Characteristics and Types of Well-test Curves of Ultra-deep and Fault-controlled Formation in Shunbei Region

ZHANG Ning, LI Zongyu, ZHANG Yun, NIE Renshi, LI Jingshun

2024, 46(4):  115-122.  DOI: 10.11885/j.issn.1674-5086.2024.02.21.01

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Fractures and sheet cave mainly develop in the ultra-deep and fault-controlled formation in Shunbei region. Horizontal well is adopted in this region to exploit the oil and gas because horizontal well can transversely pass through the fractured-caved formation. The well-test curves are complex and various. According to the middle curve characteristics after the wellbore storage and skin effects, the real well-test curves of Shunbei Region can be divided into 3 categories. The curve characteristics of the 3 categories can directly reflect the different contact relationship of horizontal well with fractures and caves. In addition, according to the late curve characteristics, the 3 categories can be further divided into 9 subcategories. The curve characteristics of the 9 subcategories differ each other and reflect different development status of fractures and caves in the periphery of horizontal well. At the end, the physical models of 3 categories and 9 subcategories, which are corresponding to the real well-test curves of 3 categories and 9 subcategories, are presented for well-test interpretations and evaluations. The research results in this article can be used to guide the work of well-test analysis and study for Shunbei region, and can also be used to guide the work of well-test study for other deep and fault-controlled formations

A Study on the Kinetic Characteristics of Tazhong Deep Heavy Oil with Different Oxygen Contents

ZHOU Daiyu, DU Xuan, DU Hongbao, YAN Gengping, LUO Hao

2024, 46(4):  123-130.  DOI: 10.11885/j.issn.1674-5086.2024.02.29.04

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The oxidation process of crude oil in oxygen-reduced air is complex. In order to accurately analyze the oxidation reaction of crude oil under reservoir conditions, it is necessary to carry out comprehensive qualitative and quantitative studies. In order to further explore the oxidation mechanism of crude oil in the process of deoxygenated air flooding, and to clarify its oxidation heat release, weight loss and kinetic characteristics, the thermal analysis experiment of Tazhong deep heavy oil reservoir in Tarim Oilfield is carried out. DSC results show that the increase of oxygen content significantly promotes the oxidation heat effect of crude oil, and the overall oxidation heat release and peak heat flow of crude oil increase greatly with the increase of oxygen content. TG experiments show that with the increase of oxygen content, the low temperature oxidation interval of crude oil keeps shortening, and the mass consumption in the low temperature oxidation stage is reduced. The temperature range of the low-temperature oxidation interval gradually narrows with the increase of oxygen content in the oxygen reduction air (the deepening of oxidation degree) during static oxidation. Based on the TG experiment data, the activation energy of crude oil in the low-temperature oxidation stage obtained with Friedman and OFW methods is close, and the activation energy increases with the increase of conversion rate. The average activation energy of crude oil used in the experiment in the low-temperature oxidation stage in oxygen reduced air with oxygen content of 5% is 81.04 kJ/mol.

A Study on the Characteristics and Mechanism of Air Displacement of Deoxygenated Air in Tazhong Deep Heavy Oil

WU Zangyuan, ZHANG Xun, LI Yang, YAO Jie, FENG Qihong

2024, 46(4):  131-137.  DOI: 10.11885/j.issn.1674-5086.2024.02.29.03

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Static oxidation experiments were carried out for the Tazhong deep heavy oil reservoir, the composition of oil and gas produced with different oxygen content and different oxidation times was analyzed, and the oxidation characteristics, oxidation pathways and oxidation mechanisms of crude oil and deoxygenated air in the process of deoxygenated air injection in the reservoir were studied. The experimental results showed that the oxygen consumption rate of crude oil was positively correlated with the oxygen content of oxygen-reduced air and negatively correlated with the oxidation time. The amount of generated carbon dioxide also increased with the increase of oxidation time and oxygen content of oxygen-reduced air. The reaction between crude oil and oxygen-reduced air can increase the viscosity of crude oil to a certain extent. The increase amplitude of viscosity was greater with higher oxygen content of oxygen-reduced air and longer oxidation time. After oxidation, the content of saturated hydrocarbons and aromatic hydrocarbons in crude oil decreased, while the content of resin and asphaltene increased, especially asphaltene. The C==O stretching vibration peak appeared in the crude oil after oxidation, and the vibration peak became stronger with the increase of oxygen content in oxygen-reduced air, indicating that the oxidation process of crude oil involved oxygenation reactions to generate substances such as aldehydes. With the increase of oxygen content, the oxidation reaction deepened continuously.

Nitrogen Injection Technology for Improved Oil Recovery in Fractured-vuggy Carbonate Reservoirs

SHE Zhicheng, CHEN Lixin, XU Sanfeng, XIAO Yun, ZHANG Jian

2024, 46(4):  138-148.  DOI: 10.11885/j.issn.1674-5086.2024.04.14.01

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The Ordovician reservoir in Halahatang is a typical fractured-vuggy carbonate reservoir. The karst reservoir is well developed, and the reservoir permeability space is mainly composed of karst caves, dissolution holes and fractures of different sizes, which are discrete in general, locally continuous, multi-scaled in reservoir collective space, and complex in morphology and distribution. Water injection and displacement are the most important development methods for this type of reservoir. After 15 years of development, the number of single wells and units with water injection failure is increasing year by year. After water flooding failure, gas injection becomes the most important means of fractured-vuggy carbonate reservoir extraction. The gas injection extraction technology has been tested and applied in Halahatang. And the six-factor gas injection well selection standard has been established. The wells are selected from six aspects, including karst background, well-reservoir relationship, drilling depth, reserve scale, production dynamics, and remaining oil type. The gas injection parameters are designed according to five aspects, including gas injection timing, gas injection method, gas injection volume, stewing time, and indicator curve. Some preliminary understandings of gas injection well selection principles and gas injection parameters design have been obtained, which is hoped to provide reference for gas injection development of fractured-vuggy carbonate reservoir.

Water Injection and Gas Injection to Enhance Oil Recovery in Yingmai 2 Fracture-vuggy Reservoir

CHEN Fangfang, PENG Debing, WANG Na, WANG Zhangheng, ZENG Qixin

2024, 46(4):  149-158.  DOI: 10.11885/j.issn.1674-5086.2024.02.22.03

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In order to solve the problem that a large amount of remaining oil has not been produced in Yingmai 2 ultra-deep fractured cavernous reservoir, a visual physical model is prepared based on the characteristics of typical reservoir structures, and physical simulation experiments of EOR with different development methods such as water injection and gas injection are carried out. By comparing the water cut and recovery efficiency at different stages, the effects of different development methods on residual oil production in Yingmai 2 fracture-vuggy reservoir are quantitatively analyzed. The feasibility of alternate development modes of water injection, gas injection and gas water after bottom water flooding is studied by using the prepared fissure-hole model and fault solution model, and the reasonable injection and production modes to further improve the recovery efficiency of Yingmai 2 fractured-vuggy reservoir are as follows: low injection and high production water injection, high injection and low production gas injection and alternate gas injection. Among them, gas-water alternation can greatly improve oil recovery. The research results can provide support for further enhancing oil recovery in Yingmai 2 fracture-vuggy reservoir.

An Experimental of “ Enhanced Foam + Gel” Flooding in High Salinity Reservoirs

FAN Xiaoyi, ZHOU Jilong, ZHOU Yongqiang, ZHANG Jintong, ZHANG Xun

2024, 46(4):  159-168.  DOI: 10.11885/j.issn.1674-5086.2024.02.29.02

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Chunguang Oilfield have entered into the development stage of high water content, high recovery and production decline. In view of the current problems such as the reduction of new reserves, the dispersion of remaining oil, and the difficulty of tapping potential, the oilfield urgently needs to a new development mode so as to further tap the potential of the remaining oil and achieve stable production of the oilfield. The experiment of “ enhanced foam + gel” flooding was carried out, and the results of different media displacement showed that the enhanced oil recovery effect of the 0.4% P2-1+0.1% warm rubber reinforced foam system was much better than that of the single media system. The results of multi-round injection experiments with different media show that when the amount of slug is the same, the more injection rounds and the more slug plugs, the higher the enhanced oil recovery, and the increase of slug can increase the coverage and permeability area of the slug system to the reservoir, thereby improving the driving effect of crude oil and increasing the oil recovery.

Reflections on Completion Engineering and Recovery of Ultra-deep Oil and Gas Wells

REN Jinming, PAN Zhaocai, HUANG Kun, FENG Shaobo, ZHANG Bao

2024, 46(4):  169-177.  DOI: 10.11885/j.issn.1674-5086.2024.06.19.02

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The continuous development of ultra-deep oil and gas reservoirs is closely related to the completion design of oil and gas wells. However, due to limitations in drilling equipment, the presence of high-pressure saline layers, geological characteristics such as prone-to-collapse and prone-to-leakage formations, as well as economic evaluation considerations, the completion methods for ultra-deep oil and gas wells exhibit significant diversity (open-hole completions, completions using small-sized reservoir casings not exceeding $\phi$127 mm, and so on). Designs featuring production strings traversing the perforation top boundary and even the perforation bottom boundary are also common, and permanent packers are often preferred. These factors can potentially increase operational difficulties, prolong operation times, elevate costs, and impact well productivity and ultimate recovery rates. By analyzing two already developed ultra-deep oil and gas reservoir blocks as case studies, it was discovered that the accumulation of sand or silt is a crucial factor contributing to low well productivity, subsequently adversely affecting recovery rates. In response, the study proposes that the research and design of ultra-deep well completions should anticipate scenarios of sand or silt accumulation. The objective is to prolong the duration of sand or silt accumulation, thereby creating favorable conditions for subsequent operations and ultimately enhancing recovery rates. To achieve this, the study conducted thorough scientific research and optimization on five key aspects: completion methods, reservoir casing sizes, completion string configurations, packer type selection, and sand pocket designs. Building upon these optimizations, comprehensive calculations were further performed for drilling and completion investments, drilling and completion cycles, and economic evaluation indicators. In cases where economic evaluation indicators fail to meet expectations, increasing single-well production is suggested as a means to resolve potential conflicts between enhancing well construction quality and meeting economic evaluations.

A Study on Cement Slurry Circulation Fluid Mixing for Deep Well Casing Cementing in the Sichuan-Chongqing Area

YANG Fujie, SUN Jinfei, XU Kewei, LUO Hanlin, LI Zaoyuan

2024, 46(4):  178-188.  DOI: 10.11885/j.issn.1674-5086.2024.03.01.03

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During the process of cement injection in deep wells, due to the influence of complex wellbore conditions such as long sealing sections, narrow gaps, and high eccentricity, the annulus fluid is prone to mixing, and the mixing may increase the friction of the mixed section, causing cementing leakage. In order to solve the problem of inaccurate ECD prediction of high eccentricity annulus in the casing cementing operation of the oil layer in the Gaomo in eastern Sichuan, a cementing fluid mixing simulation and an experimental study on the rheology of the slurry were carried out. The study calculated the slurry in real time based on CFD. According to the changes in the fluid proportion of each section, the wellbore ECD was calculated by fitting the rheological equation through rheological experiments. The results proved that the eccentricity is the main factor affecting the change of the mixing ratio. When the eccentricity is low, the proportion of drilling fluid, spacer fluid and cement slurry is 5：1：4, and when the eccentricity is high, the ratio is mainly 7：1：2; the ECD of the mixed grout is 0.2$\sim$0.8 g/cm$^3$ higher than the conventional ECD in the upper grouting section, and is 0.2$\sim$0.5 g/cm$^3$ higher in the lower pure cement section. This study reveals the impact of complex well conditions in deep wells on the mixing ratio between fluids and the equivalent density of the wellbore. It is of great significance to ensure the safe cementing operation of deep wells in Sichuan and Chongqing and improve the quality of cementing.