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Research Status and Prospect of Artificial Intelligence in Reservoir Fracturing Stimulation
SHENG Mao, LI Gensheng, TIAN Shouceng, LIAO Qinzhuo, WANG Tianyu, SONG Xianzhi
Abstract515)      PDF (3060KB)(527)      
In view of the development needs of oil and gas reservoir fracturing stimulation technology, the research status of artificial intelligence (AI) in fracturing stimulation is described, the key theoretical problems in the development of AI in fracturing are analyzed, and the future main research directions and application scenarios are prospected. At home and abroad, some progress has been made in fracturing design optimization, fracturing condition diagnosis and risk pre-warning,fracturing flowback optimization control. But it is still in the transition stage from academic research to industrial application, facing with the key theoretical problems including small sample size and lack of label data, poor model interpretability and the requirement of deep integration of datadriven and physical models. Based on the existing problems, the main research directions of artificial intelligence for fracturing in the future are prospected in this paper, such as data management and feature engineering, deep mining of fracturing data in small sample learning scenarios, interpretable fracturing intelligent algorithms based on knowledge embedding and knowledge discovery, and dynamic optimization of fracturing parameters and risk pre-warning and control methods based on reinforcement learning, etc. Three application scenarios are suggested, including intelligent optimization of fracturing design, closed-loop control of fracturing construction, and intelligent control of fracturing flowback, aiming for the high-quality balanced fracture formation and safe fracturing.
2022, 45 (4): 1-8.    doi: 10.3969/J. ISSN.1006-768X.2022.04.01
Study and Application of Managed Pressure Technology of Running Casing in Narrow Safety Density Window Formations
YANG Yun, CHEN Qian, WEI Haifang, WANG Peifeng, TANG Tao, PENG Yuanchao, MA Tianshou, WANG Ling,
Abstract302)      PDF (1582KB)(272)      
In the process of running casing in the narrow safety density window formations, the surge pressure generated by the movement of the casing string in the borehole can easily induce the complicated downhole incidents. In order to ensure the safety of running casing under narrow safety density window, a transient surge pressure calculation model for casing running in eccentric annulus was proposed. The wellbore pressure prediction and management model during the liner running was also proposed based on the wellbore pressure balance relationships. The main influencing factors of bottom hole surge pressure in running casing operation were analyzed and the case study of field running casing for managed pressure cementing was performed. The research results show that the casing running speed, casing eccentricity, and rheological parameters of drilling fluid are the main factors affecting the bottom hole surge pressure. The annulus transient surge pressure increases with the increasing of annulus fluid rheological parameters (yield value, consistency coefficient and fluidity index) and casing running speed, but decreases with the increasing of eccentricity. A case calculation was carried out by taking Well DB-X as an example, and the wellbore pressure control chart of running casing for managed pressure cementing was proposed. The calculation results show that it can effectively guarantee the bottom hole safety when keeping the liner running speed of 0.16~0.20 m/s. The data guide this well operation, effectively prevent the occurrence of downhole complications during casing running. The results of this paper can provide a new idea for velocity optimization of running casing and bottom hole pressure management during cementing, which is of great significance for reducing casing running risk and improving cementing quality in formation with narrow safety density window. 
2022, 45 (3): 1-8.    doi: 10.3969/J. ISSN.1006-768X.2022.03.01
Drilling Practice and Understanding of Ultra-long Horizontal Section Wells of Shale Gas in Sichuan Basin
FU Qiang
Abstract251)      PDF (1633KB)(513)      
Ultra-long horizontal well with horizontal section over 3 000 m has great advantages in improving single well production and economic benefits. With the development of this technology, it will gradually become the main direction in shale gas, tight oil and other developments. In view of the drilling difficulties of ultra-long horizontal wells of shale gas in Sichuan Basin, the key technologies for ultra-long horizontal well are developed, which include the optimization of wellbore structure, the strengthening of drilling parameters, the optimization of drilling fluid system and borehole cleaning, the geo-engineering integrated steering drilling, the casing running and cementing technology in horizontal section. This paper summarizes the practices and successful cases of horizontal shale gas wells with horizontal section over 3 000 m. On this basis,the development suggestions and directions for horizontal shale gas wells with ultra-long horizontal section in the future are pointed out, such as the further exploration and development of low-cost drilling technology, research of safe and efficient optimal fast drilling technology, efficient cooperation of geo-engineering integration, and improvement of project management under daily rate system, which is aiming at promoting the drilling technology development for horizontal shale gas wells with ultra-long horizontal section and cost-reducing and benefit increasing development in China.
2022, 45 (4): 9-18.    doi: 10.3969/J. ISSN.1006-768X.2022.04.02
Advances of Experiment and Numerical Simulation Researches on Proppant Transport for Unconventional Reservoir Fracturing
GUO Jianchun, ZHOU Hangyu, TANG Tang, ZHANG Tao,
Abstract184)      PDF (2501KB)(234)      
Unconventional hydrocarbons have become significant resources to ensure energy security of our country, and the large scale volume fracturing technology for horizontal wells is a critical method for developing unconventional reservoirs economically. Because of the differences of such parameters as fracturing fluid, proppant, pumping rate and others between conventional and unconventional fracturing, the characteristics of proppant transport and placement are completely different. Starting from the search for the typical characteristics of proppant transportation in unconventional reservoir fracturing, the paper summarizes the domestic and international research outcomes of proppant transportation experiments and numerical simulations in recent years, expounds the laws of proppant transportation, placement and diversion in single fracture and complex fracture network, and evaluates the applicability and limitations of the numerical methods based on computational fluid dynamics. On this basis, the unconventional reservoir fracturing proppant transport simulation is discussed, and points out that the rough fracture fracturing fluid simulation experiment device, fracturing fluid-proppant velocity characterization test method, numerical simulation method for coupling of fracture-fluid-proppant, and other key issue will be the next research direction, so as to provide theoretical guidance for efficient stimulation of unconventional oil and gas reservoirs.  
2022, 45 (3): 48-54.    doi: 10.3969/J. ISSN.1006-768X.2022.03.09
Research and Application of Electromagnetic Wave Wireless Transmission Technology in Oil and Gas Well
Abstract164)      PDF (2289KB)(249)      
In oil and gas production wells, due to the shielding influence of metal casing, the signal of electromagnetic wave wireless transmission will be greatly weakened or discontinuous, which affects the popularization and application of electromagnetic wave wireless transmission technology in production wells. Aiming at this problem, the wireless transmission mechanism of electromagnetic wave in cased well was studied in this paper, the polarization phenomenon caused by electromagnetic wave passing through casing was avoided by using magnetic current loop excitation technology to form a current loop between oil sleeves, which effectively solved the electromagnetic wave shielding problem. The field test shows that the dynamic data representing the downhole state in oil and gas production wells can be transmitted to the surface in real time through the wireless transmission technology of electromagnetic wave. The signal is clear and stable, providing technical means for production companies to master dynamic data such as downhole temperature, pressure and water cut of oil and gas production wells in real time. It provides scientific basis for reservoir rapid evaluation and production system optimization,and has broad application prospect.
2022, 45 (4): 19-25.    doi: 10.3969/J. ISSN.1006-768X.2022.04.03
Abstract154)      PDF (1201KB)(150)      
2022, 45 (3): 156-.
Precise Managed Pressure Cementing Technology Application in Sichuan, Chongqing and Tarim Basin
SUN Yicheng, JIANG Lin, LIU Chenggang
Abstract153)      PDF (1517KB)(237)      
At present, the cementing of deep, ultra-deep and complex wells are often faced with such challenges as long sealing sections, narrow safety density window of drilling fluid in the same open hole section,small annular clearance, low casing centralization, malignant well loss or even total loss at wellhead with conventional cementing process, cement slurry unable to return to the predetermined position, poor cementing quality and high risk of well control. In view of the narrow density window cementing in Moxi-Gaoshidi structure, Longgang structure, Shuangyushi-Hewanchang structure and Pied-Tarim structure, the paper proposes to adopt the precise managed pressure cementing technology. With?the?precise managed pressure cementing equipment?and?related?software to control the bottom hole pressure during cementing operation, realize real-time dynamic calculation of wellbore pressure to reduce the error of manual calculation, precise control downhole pressure under the condition of narrow density window with loss and blowout co-existing, ensure the wellbore to be in stable and leak-proof state without any blowout or overflow, thus improve the cementing quality. At present, this technology has been popularized and applied in Sichuan and Tarim area, has become a key technology to solve the problem of high quality cementing in such complex formations, providing a reference for improving cementing quality of similar deep and ultra-deep wells and complex formations in other regions at home and abroad.    
2022, 45 (3): 15-20.    doi: 10.3969/J. ISSN.1006-768X.2022.03.03
Abstract151)      PDF (562KB)(190)      
2022, 45 (6): 170-.
Development and Application of New Type Cementing Stage Collar with Packer
Abstract148)      PDF (1263KB)(154)      
In Tarim basin, it is difficult to use conventional cementing to seal 4000~5000m deep and ultra-deep wells at a time, so hierarchical cementing technology is often used for construction. Due to the well developed leakage-prone formations, there are problems with conventional stage collar for two-stage cementing such as loss of primary cementing and total loss of secondary cementing, which lead to the long length of free casing section and affect the cementing quality. In order to solve the above problems, a new type stage collar with packer was developed. This tool includes a stage cementing collar,a injection valve and a hydraulic expansion packer. On the basis of the completion of the staged cementing operation, the function of packer expansion after the first stage cementing is added, which can effectively seal the annulus between casing and open hole during secondary cementing, reduce the probability of secondary cementing loss, and increase cement top. The results of laboratory tests and field application show that the tool is safe and reliable with no loss during the secondary cementing process, improving the cementing quality and saving cost. This tool provides a powerful technical guarantee for cementing the low-pressure and easy-loss long-seal section, and has a broad application prospect.
2022, 45 (3): 104-108.    doi: 10.3969/J. ISSN.1006-768X.2022.03.19
Research and Application of Acidification Process for Horizontal Wells in Huaqing Chang 6 Reservoir
ZHAO Xiaoguang , HU Dongwei , LI Libiao , TU Xuewan , HUANG Yan, SUN Zhicheng
Abstract146)      PDF (1126KB)(204)      
The Chang 6 reservoir is the main production layer of Huaqing oilfield, which is a typical ultra-low permeability reservoir with poor reservoir physical properties and great difficult in development. The application of horizontal well development technology has effectively increased the average single well production of the reservoir. However, in the actual development process, many horizontal wells have experienced a significant decline in production. In order to stimulate these low-yield horizontal wells, starting from the geological characteristics of the reservoir of Chang6 reservoir in Huaqing oilfield, the feasibility of the acidification process of the oil reservoir was demonstrated, and then the acidification process of the horizontal well was designed and optimized based on factors such as the production dynamics of the well. The research work of selecting the acid system, optimizing the acid formulation, designing and optimizing the acidification process parameters, and designing the acidification tools and string have been carried out, and the experimental application has been carried out in the field. The conventional stimulation and excavation process of horizontal well in Chang6 reservoir in Huaqing oilfield has been usefully explored and practiced, and the acidification process of horizontal well with Huaqing characteristics has been preliminarily formed, which provides strong support for the development and stable production of Huaqing oilfield.
2022, 45 (4): 165-169.    doi: 10.3969/J. ISSN.1006-768X.2022.04.28
Experimental Study on Migration and Plugging Pattern of Knot Temporary Plugging Agent
WU Baocheng, , ZHOU Fujian , WANG Mingxing, ZHOU Peiyao, LV Wenjing , WANG Bo
Abstract144)      PDF (5730KB)(241)      
Perforation plugging is the key to the success in the multi-cluster temporary plugging fracturing in Mahu conglomerate reservoir. It is effective to clarify the migration characteristics and the plugging pattern of the plugging agent to guide the perforation plugging. In this paper, a new type of knot temporary plugging agent is proposed to plug the hole, and a large-scale visual migration observation system of the temporary plugging agent is established. The migration characteristics of spherical temporary plugging agent and knot temporary plugging agent are compared and studied, and the advantages of knot temporary plugging agent are pointed out. The influence law of the number of holes and pumping capacity on the perforation plugging is further studied. Based on the experimental research results, a multi-cluster fracturing knot temporary plugging experiment was carried out in the horizontal well section, and the reliability of the knot temporary plugging agent was verified by combining with the downhole video monitoring results. The results show that the unique two-wing structure of the new type of knot temporary plugging agent keeps a good suspension state during migration and is easy to enter the hole. The middle spherical knot structure ensures that the perforation can be plugged under high pressure. The research results of this paper have certain guiding significance for the scheme establishment of the multi-cluster temporary plugging fracturing in horizontal well section.
2022, 45 (4): 61-66.    doi: 10.3969/J. ISSN.1006-768X.2022.04.10
Status Quo and Improvement Suggestions of Automatic Monitoring Equipment for Drilling Fluid Performance
Abstract139)      PDF (3815KB)(234)      
Drilling automation is an inevitable trend in the development of petroleum industry, and the automatic monitoring technology of drilling fluid performance has become the focus of the industry. Currently it is basically rely on artificial drilling fluid performance monitoring, but manual sampling is with a security risk and error of manual monitoring, manual or input software analysis and calculation may lead to drilling fluid performance data for the decision-making on serious lag problems, so it is in urgent need of drilling fluid automatic monitoring equipment developed for real-time online monitoring of drilling fluid performance so as to timely perform drilling fluid performance maintenance and avoid downhole complications. In this paper, the real-time drilling fluid monitoring equipment and technology that has been successfully developed or applied in the field at home and abroad are investigated in detail. The results show that the real-time drilling fluid monitoring system at home and abroad generally has problems such as incomplete monitoring function, large volume and high price. In view of the above problems, it is proposed that the real-time drilling fluid monitoring equipment should expand its monitoring function, improve the degree of automation, optimize the monitoring method and improve the monitoring accuracy, and develop miniaturized equipment and integrated equipment in the future.The development of online monitoring technology will lay a foundation for the realization of comprehensive digitization of drilling and the intelligent development of drilling in the future.
2022, 45 (3): 42-47.    doi: 10.3969/J. ISSN.1006-768X.2022.03.08
Personalized Design of Efficient PDC Bit for Highly Abrasive Sandstone Formation in Northeast Sichuan Basin: A Case Study of Shaximiao Formation in Wubaochang Block
RONG Zhun , DENG Xu, ZHANG Qi , CHEN Pengju, YAO Jianlin, ZHANG Yang , YAN Shuang
Abstract138)      PDF (1912KB)(175)      
The tight sandstone reservoir of the second member of Shaximiao Formation in Wubaochang block in northeast Sichuan basin has high unconfined compressive strength and strong abrasive property, which leads to low ROP and short footage for single bit. Meanwhile, the non-productive time ( NPT) caused by frequent tripping, waiting and bit replacement is too long, seriously restricting drilling speed increasing. The rock characteristics of the second member of the Shaximiao Formation in the Wubaochang block was firstly studied in this paper. Then the wear conditions of the bits used in the completed horizontal well sections in the field were analyzed, and based on the analysis, the corresponding suggestions for the subsequent personalized bit design was put forward. Finally, according to the characteristics of the reservoir rock and the field application of the bit, and through the targeted cutter design and simulation research on the PDC bit-rock interaction, the force balance analysis and optimization were carried out, and finally a seven blade personalized PDC bit mainly for the highly abrasive sandstone formation in Northeast Sichuan is developed. The field application results show that the average footage of the designed bit is increased by 69% and the average ROP is increased by 68% compared with other bits.
2022, 45 (4): 32-37.    doi: 10.3969/J. ISSN.1006-768X.2022.04.05
Bit Optimization of Deep Complex Lithological Formations in Jidong Oilfield
XU Xiaofeng , LI Yunfeng , WANG Changhao, LI Shibin, SONG Wei , ZHOU Yan , CHEN Chunlai
Abstract138)      PDF (4859KB)(80)      

The lithology of deep strata in Jidong Oilfield is complex with high hardness, strong abrasiveness and extremely inhomogeneity, resulting in a short average footage and life of the PDC bits, which seriously restricts the drilling efficiency. In order to solve this problem, the rock X-ray diffraction experiment was carried out to obtain the mineral composition, hardness and plasticity coefficient of the rock. Combined with the drillability test results of PDC bit and roller bit, the drilling resistance profile of deep formation was established. Then, the mechanical model of formation-PDC drill bit under the condition of rock cutting was established. The stress state of single cutter in rock cutting was analyzed, showing that with the increase of the back angle, the axial force increases first and then stabilizes, while the lateral force appears an inflection point. According to the results of drilling resistance test and numerical simulation, when the optimal dip angle is 15 ° and the optimal nozzle combination is two 16 mm central nozzles plus five 14 mm peripheral nozzles, the drill bit is conducive to crushing tight mudstone and hard interlayer, and the rate of penetration is significantly increased, which is of great significance to ensure the continuous speed increase and cost reduction of Jidong Oilfield.

2022, 45 (5): 22-28.    doi: 10.3969/J. ISSN.1006-768X.2022.05.04

Key Techniques Practice of Drilling Speed Improving in Pengzhou Marine Ultra-deep Horizontal Well

XU Hao, TANG Honglin, WANG Huaping, DONG Bo, ZHENG Yi
Abstract130)      PDF (2406KB)(136)      
 Pengzhou marine area of west Sichuan gas field is rich in natural gas resources, due to the deep burial of the reservoir, poor drillability of the formation, developed fracture and pore and other reasons, it is usually suffered from downhole failures and long drilling cycle in the process of drilling. In view of this, based on the analysis of regional engineering geological characteristics and drilling technical difficulties, such researches have been carried out in this paper as pre-bending ant-deviation and straightening technology, wear-resistant conical PDC bit optimization technology, parameter strengthening technology based on MSE, composite footage maximization technology, selection of friction reducing and speed increasing tools, anti-collapse drilling fluid system in karst formation, forming the key technology of improving drilling speed of marine ultra-deep horizontal wells. Relevant technologies have been integrated and applied in three ultra-deep horizontal wells such as Well PZ3 -5D. Compared with the early completed vertical wells in this region, good drilling results had been achieved although the drilling difficulty increased significantly. The ROP was increased by 102. 76% , the drilling cycle was shortened by 25. 87% . It provides valuable experiences for the fast drilling of marine ultra-deep horizontal wells in Western Sichuan Gas Field.
2022, 45 (5): 16-21.    doi: 10.3969/J. ISSN.1006-768X.2022.05.03
Technical Status and Application for Annulus Injection of Aerated Drilling Technology
ZHU Lihua, FAN Liming, HAN Liexiang, LI Zhiling, DENG Yuhan, LI Xue,
Abstract130)      PDF (1798KB)(157)      
In the depleted and low-pressure reservoirs, it is easy to be encountered with such problems as fluid total loss,differential pipe sticking and reservoir damage during conventional drilling operations, and even with contradiction between wellbore stability and reservoir protection. In view of the above problems, a detailed study on the technical status and applications for domestic and foreign aerated underbalanced drilling technology with annulus injection was conducted. Such technical problems as severe loss, differential stuck pipe and low drilling rate can be effectively solved with the aerated drilling technology with annulus injection, and precise directional drilling of horizontal wells can be achieved by using conventional drilling fluid pulse MWD /LWD, which meanwhile can protect the reservoir and increase single well production. In mature fields, by combining aerated drilling and managed pressure drilling, the aerated drilling technology with annulus nitrogen injection has been successfully performed in sulfur-bearing, fractured and depleted low pressure high temperature reservoirs, which not only protects the reservoir, but also avoids reservoir leakage and meets the requirements of well control. Field application shows that the aerated drilling technology with annulus nitrogen injection can not only protect reservoirs, but also reduce downhole incidents and drilling cost, having a wide application prospect in the drilling of low-pressure, fractured and unstable reservoirs and helping to solve the technical challenges on the efficient development for low pressure depleted reservoirs, providing reference significance for the development of managed pressure drilling technology for horizontal wells in low pressure depleted reservoirs in China.
2022, 45 (6): 1-6.
Study on Wellbore Temperature Field of Shale Gas Horizontal Well Drilling in Y101 Block
ZHANG Peiyu , WEN Bo, WANG Lijia
Abstract125)      PDF (1990KB)(146)      
The failure and damage of downhole tools caused by the high temperature occur frequently in Y101 block. In order to clarify the wellbore temperature field of shale gas drilling in Y101 block, based on the thermodynamic theory, a new model of wellbore temperature field of deep shale gas horizontal well drilling that comprehensively considers the influence of mechanical and hydraulic heat source terms is established, and the influencing factors are analyzed, the main control factors affecting the bottom hole temperature are clarified, and cooling measures have been proposed. The prediction results of the new model are in good agreement with the existing model and field measurements,and the error bars within ± 5% . After considering the influence of the heat source term, the maximum annulus temperature is located near the bit, and the maximum temperature is greater than the original formation temperature,and the temperature difference increases with drilling time. The temperature difference increases linearly with the increase of drilling fluid yield, weight on bit, rotating speed and injecting temperature,and increases in a power function with the increase of drilling fluid plastic viscosity and density. When the length of the horizontal section is less than 1 000 m,the ground cooling effect is good,and when exceeds 1 000 m,the decreasing of mud density is better than that of ground cooling. After applying of mud density reduction and ground cooling, the maximum bottom hole temperature is reduced by 6 ℃ , rate of penetration is increased by 67. 51% , with remarkable effect of cooling,drilling speed and efficiency improving. The research results in this paper provide theoretical support for the bottom hole cooling in the Y101 block, and provide a strong guarantee for the efficient exploration and development for deep shale gas. 
2022, 45 (5): 1-7.    doi: 10.3969/J. ISSN.1006-768X.2022.05.01
Application of Drag and Torque Analysis in the Design of Horizontal Wells
WANG Zhirui
Abstract124)      PDF (1418KB)(208)      
The influence of drag and torque on horizontal well drilling is very great, which determines whether tripping and drilling can be performed normally. Therefore, the drag and torque analysis in advance in the design of a horizontal well plays a positive role in the successful drilling operations. This article introduces main research contents involved in drag and torque analysis. The effects of drag and torque on buckling, Von Mises stress, side force and torque of drilling tool are checked in this paper. That means that no buckling occurs during sliding drilling if the safety factor for Von Mises check is above 1 . 67, that is, less than 60% of the yield limit, the side force must be within the allowable range, that is, less than 1 000 N /m, and the torque must be less than 90% of the maximum torque limit of drill pipe recommended by IADC. The article uses actual cases to illustrate the specific methods and steps for the drilling tool buckling check, Von Mises stress check, side force check and torque check during slide drilling and rotary drilling with PDM in the curve section, and rotary steerable drilling in horizontal section during the drag and torque analysis. Additionally, how to calculate the maximum well depth that the PDM drilling assembly can accomplish slide drilling is also stated. Through the analysis of actual drilling effect of cases, it is considered that the drag and torque analysis is an indispensable tool for the feasibility demonstration of the drilling assembly of horizontal well in the drilling design stage, and is the basic guarantee of safe, high-quality and efficient drilling. It can provide references significance for domestic drilling design departments and directional well technical service companies in horizontal well design.
2022, 45 (6): 7-13.
Development and Enlightenment of Re-fracturing Technology for Horizontal Shale Gas Wells in North America
DONG Sha, JING Chen, SONG Wenjing, YANG Lei, LUO Yuxuan, DUAN Yang
Abstract118)      PDF (1107KB)(239)      
 As the rapid decline of production in horizontal shale gas wells and high cost of drilling new ones, re-fracturing can restore and increase the production of horizontal shale gas wells with good economic benefits. When conducting stimulation for the first time, the output of horizontal wells may be with low production due to improper well placement, poor completion design and damages during production. All this can be improved through re-fracturing. The re-fracturing technology for horizontal shale gas wells has been widely used in North American and is mature. This paper summarizes the technical difficulties in re-fracturing operations in horizontal shale gas wells in North America, well placement optimization, and re-fracturing technology and tools. Finally, in view of the re-fracturing for horizontal shale gas wells in Sichuan Basin, combined with the current research results and future development trend of relevant technologies, some suggestions are put forward, including carrying out re-fracturing pilot test, avoiding general fracturing to achieve precise stimulation, using supercritical CO 2 as fracturing fluid to instead of water-based fracturing fluid. With the development of some shale gas plays gradually entering the middle and late stage, re-fracturing will become an important method for old well production enhancing.A set of shale gas horizontal well re-fracturing technology adaptive to China will also be developed, which will play a key role in reducing cost and increasing efficiency in China’s shale gas development.
2022, 45 (4): 98-102.    doi: 10.3969/J. ISSN.1006-768X.2022.04.16
Faust Improved Algorithm for Formation Acoustic Time Difference and Its Application
WANG Pan, HU Yitao, LIU Ting, CHENG Leli
Abstract116)      PDF (1839KB)(145)      
LWD logging data are commonly used in formation pore pressure monitoring and calculation. However, in the process of formation pore pressure monitoring, LWD data are often undetectable due to engineering reasons or missing due to formation reasons. Therefore, Faust formula is often used to fit the LWD. Practice shows that the relative error between the fitted acoustic time difference and the measured acoustic time difference is more than 5%. Therefore, this paper improved the traditional Faust formula by removing the vertical depth parameter in the traditional Faust formula and changing the formula. The offshore drilling practice concluded that the relative error between the acoustic time data calculated by the improved formula fitting calculation and the measured acoustic data can be controlled within 5%, and the formation pressure coincidence rate calculated with the fitting of acoustic time is of over 97%, which can meet the demand of field operation, and this formula can be also used for LWD tool logs and wireline tool logs. 
2022, 45 (3): 9-14.    doi: 10.3969/J. ISSN.1006-768X.2022.03.02