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Liu, Jingshou (China University of Petroleum, East China) | Ding, Wenlong (Shandong Provincial Key Laboratory of Deep Oil and Gas) | Yang, Haimeng (and Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources, Institute of Geology, Chinese Academy of Geological Sciences (Corresponding author) | Liu, Yang (email: email@example.com))
Summary Fractured reservoirs account for more than one-half of the global oil and gas output and thus play a pivotal role in the world’s energy structure. Under diagenesis, rocks become dense, and tectonic fractures easily form under subsequent tectonic movement. These tectonic fractures are the main seepage conduits of tight sandstone reservoirs and are important determinants of whether a tight sandstone reservoir can have high, stable oil and gas production. The influence of multistage tectonic movement has led to well-developed fractures in the Ordos Basin in central China. In the process of reservoir development, the effective stress on the fracture surface increases because of the decrease in pore pressure, and the fracture aperture, porosity, and permeability also change accordingly. Therefore, modeling of the dual porosity and dual permeability of fractured reservoirs requires a dynamic 4D modeling process related to time. In this paper, we propose a 4D modeling method of dual porosity and dual permeability in fractured tight sandstone reservoirs. First, the porosity and permeability distribution of the reservoir matrix are established based on reservoir modeling. Based on geomechanical modeling, the density and occurrence of natural fractures are predicted by the paleostress field. The in-situ stress field is used to analyze the fracture aperture, and the variation in the fracture aperture during the development process is analyzed along with the variation in the in-situ stress in the development process to realize 4D modeling of the porosity and permeability of fractured reservoirs. The total porosity of the fracture is 0 to 8 × 10%, and the principal value of the planar permeability of the fracture is 0 to 3 × 10 µm; the principal value of the fracture permeability is concentrated in the direction of 65 to 70° east-northeast. The simulated fracture porosity stress sensitivity index is distributed between 0 and 0.2, and the fracture permeability stress sensitivity index is distributed between 0 and 0.4. The Young’s modulus of the rock, in-situ stress parameters, and sound velocity in the rock are important factors affecting the fracture stress sensitivity.
Chen, Yong (Oil&Gas Technology Research Institute, Changqing Oilfield Company, Petrochina) | Xie, Yonggang (Oil&Gas Technology Research Institute, Changqing Oilfield Company, Petrochina) | Tian, Wei (Oil&Gas Technology Research Institute, Changqing Oilfield Company, Petrochina) | Wang, Xiongxiong (Oil&Gas Technology Research Institute, Changqing Oilfield Company, Petrochina) | Zhao, Zhengyan (Oil&Gas Technology Research Institute, Changqing Oilfield Company, Petrochina) | Xiao, Shuqin (National Engineering Laboratory for Exploration and Development of Low Permeability Oil&Gas Fields)
Abstract An intermittent gas well intelligent production technology is presented that use intelligent methods to determine and optimize the intermittent system of intermittent gas wells and use newly developed remote pressure-controlled well opening equipment that can simulate manual operations and corresponding intelligent control systems. This new approach is based on the research and application of intelligent technology in the production of intermittent gas wells. By establishing the models of gas flow in different types of gas wells, combined with the historical data of typical gas wells, the optimal pen and shut-in well time chart is finally formed. A series of remote pressure-controlled well opening equipment have been developed to replace manual pressure-controlled open well operations at the well site. Through intelligent integration of well site equipment and remote control platforms, an ntermittent gas well intelligent production management system is established. The quantitative determination of the intermittent system of different types of gas wells is realized. The effectiveness of gas well intermittent measures has increased from 72% to 90%. Electromagnetic remote-controlled open well equipment with adaptive decompression and full-open cylinder structure is developed, and can meet the requirements for rapid opening of type Il intermittent gas wells. Needle-valve type remote-controlled open well equipment embedded with intelligent well drilling algorithm is developed, and the fine well opening of class I and Il intermittent gas wells is realized. Hands-free operation is realized, and the workload of operating staff on the well site is reduced by more than 15%. On-site diagnosis of gas well production status, intelligent generation of systems, intelligent analysis and optimization are realized, and intermittent gas wells are transformed from manual management to intelligent management. An intermittent gas well intelligent production management system is established to achieve intelligent management of intermittent gas wells. Complete intermittent gas well intelligent production technology for low ermeability gas fields is described in detail to permit global similar gas field reference. The novelty of the technology lies in the use of intelligent methods to solve the production problems of intermittent gas wells, including reducing the labor intensity ofemployees, improving production efficiency, improving the fine management level of tight gas field gas wells, and reducing the impact of human activities on the natural environment.
Abstract Lost circulation is a complicated situation in the drilling operation, wasting a lot of time and mud during processing. A serious lost circulation can cause hazards, such as sticking, blowout and collapse of well. There are some problems in conventional plugging technology, such as particle size of plugging material does not match crack width, slip of the blocking zone, and weak adhesion of lost circulation additive to the rock, which restricts the success rate of lost circulation operation. Regular and elastic polyhedron structure material compounds elastic variable network plugging material and rigid plugging materials to form a loss circulation materials (LCM)plugging mixture for different leakage speed and crack width affected by stress. Through plugging and HTHP sand bed experiment loss circulation materials(LCM) and amount of gel were optimized and improved. Through indoor simulation about leakage process of different leakage speed and different crack sizes, the on-site construction formula suitable for wells under different temperature is formed and determined. Scanning electron microscope shows the plugging gel has a variable network structure. By changing the ratio of elastic plugging material, rigid plugging material and gel, a LCM plugging formula for high temperature and high pressure formations can be formed to meet the pressure requirement of 7.5MPa. Leakage simulation formed on-site plan under different leakage rate to adapt to 180°C. The novel CPM material has been well-field tested and used for HPHT reservoirs. When the rate of leakage less than 30 m/h and 30-60 m/h, success rate of single plugging is more than 95% and rate of leakage greater than 60 m/h success rate of single plugging beyond 80%. Leakage loss time is more than 80% shorter than conventional plugging techniques.
Gao, Jichao (China Oilfield Services Limited) | Yang, Shuhui (COSL-Expro Testing Service Tianjin Co Ltd) | Yang, Guowei (China Oilfield Services Limited) | Shao, Shangqi (China Oilfield Services Limited)
Flow back fluid during matrix acidizing in carbonates reservoir has the characteristics of complex composition, variable physical and chemical properties, high content of crude oil and suspended solids. If discharged directly to the ground, it will cause serious environmental pollution and waste resource. A novel and environmentally friendly treatment method to solve this problem has been developed by optimizing surface flow back process, selecting chemicals, modifying filter types and equipment structure. The overall treatment strategy is to separate oil, gas, water and solid phase, inject dehydrated crude oil into pipeline, ignite gas, discharge water after meeting the requirements of industrial wastewater discharge standard, and treat solid phase harmlessly. Some problems such as emulsification, foam fluid and organic scale have been solved by optimizing acid recipe and adopting new chemicals. This novel technique successfully solved the environmental pollution problem and has high economic benefits.
Wang, Xiangzeng (Shanxi Yanchang Petroleum, Group Corp. Ltd.) | Zhang, Lei (Shanxi Yanchang Petroleum, Group Corp. Ltd.) | Zhang, Tao (China University of Petroleum) | Qiao, Xiangyang (Shanxi Yanchang Petroleum, Group Corp. Ltd.) | Wang, Yongke (Shanxi Yanchang Petroleum, Group Corp. Ltd.) | Zhao, Xisen (Shanxi Yanchang Petroleum, Group Corp. Ltd.) | Li, Xiangfang (China University of Petroleum, Beijing)
Yan’an gas field is a typical tight sandstone reservoir with multiple gas layers, large vertical span, variable size of effective sandbody, high heterogeneity, and complex surface ground environment. Due to the depositional background including both continental and marine face, the tight gas reservoir shows marginal characteristics with low porosity/permeability, thin sandbody thickness and low lateral continuity. If the field is recovered by the current mainstream technology "horizontal drilling+multi-stages hydraulic fracturing", the subsurface reserves will not be controlled fully, resulting in low economic benefit. With over a decade of practice, a cost-effective hybrid well pattern adapted to each layer and each region was formed which shows its efficiency in development of Yan’an gas field. In the hybrid well pattern, directional (vertical) well is adopted to fully control the reserves of the four main gas-bearing layers, while horizontal well is adopted to maximize the production for the reserve-enriched layers. Unlike the uniform well spacing for the marine tight gas reservoir, the well spacing in Yan’an gas field is non-uniform to adapt the strong heterogeneity in terms of storage and percolation, and the methodology to quantify the well spacing according to the local reservoir property was discussed in detail. To decrease the sand-lost drilling risk in such a low sand-continuity reservoir, the strategy named "sand recognition while drilling" is proposed for the well placement. The mathematical models for designing the directional (vertical) wells and horizontal wells are also presented in this work. In addition, the non-technical factors such as loess plateau topography and coal/water/oil resources overlay give large difficulties to open the well site and extended reach wells are required, and the criterion in selection different types of well group was given mathematically as well. The above factors in constraint the well pattern are summarized with property constraint, local constraint, macro constraint and environment constraint. The hybrid well pattern successfully unlocked and maximized the marginal gas field.
MEMS sensors have been available for seismic applications since the early 2000s. Although the 1st generation of MEMS had a proven track record of success, in particular for 3C applications, it had some difficulty in 1C to compete in terms of cost with sparser acquisitions using arrays, and to meet the requirements of the trend towards low-frequencies due to noise performance at the lower end of the spectrum. The latest generation of MEMS, however, has overcome these limitations and indeed shows additional benefits over geophones. The digital fidelity offered by the sensor enables the recording of seismic data with true amplitude and phase and in contrast to geophones its response is unaffected by manufacturing tolerances, ageing and temperature. In addition, having power consumption and cost now lower than that of a geophone connected to an ADC, these sensors are excellent candidates to complement the industry’s growing use of nodal acquisition in land surveys. For OBN applications these 3C MEMS sensors provide excellent vector fidelity with a native true vertical Z component. Two field tests, in land and OBN, were recently organized to illustrate the advantages of MEMS over geophones. The results of the two tests are herein presented and discussed. Presentation Date: Wednesday, October 14, 2020 Session Start Time: 1:50 PM Presentation Time: 1:50 PM Location: Poster Station 9 Presentation Type: Poster
Yijun, Wang (BGP, CNPC) | Yubin, Du (Changqing Oilfield, CNPC) | Yabin, Guo (BGP, CNPC) | Linke, Zhang (BGP, CNPC) | Yang, Gao (Changqing Oilfield, CNPC) | Dahong, Chen (BGP, CNPC) | Peng, Wang (BGP, CNPC)
The tight sandstone gas reservoir in Ordos Basin is characterized by “thin reservoir, low porosity, low permeability, low pressure, low abundance and strong heterogeneity”, together with low single well production, rapid pressure drop, facing the problems such as stable production and development. In order to develop geological reserves efficiently, horizontal well is widely used in this area. The characteristics of tight sandstone gas reservoir determine that fracturing is the inevitable choice for its economic development. In the past, the fracturing schemes were only determined by “one hole view”, which was lack of deep understanding of reservoir in the area surrounding boreholes. Therefore fracturing schemes were insufficient and economical enough. In order to solve the problems above, a set of seismic methods has been created. Firstly the method of multidimensional analysis of rock physics is used to optimize the geophysical parameters that are sensitive to the gas bearing property of the reservoir. Secondly pre-stack gather data with high quality are obtained by using the processing technology of the relative amplitude of the wide azimuth and the OVT (offset vector slice). Thirdly the spatial distribution of the reservoir is predicted by using the pre-stack elastic inversion. And Combined with the three-dimensional visualization technology, the reservoir distribution of surrounding area of the borehole is determined, which will guide the optimization of fracturing location and direction and scale, so as to perfect the fracturing reconstruction scheme. The set of methods has obtained a good result in Shaan* block of Sulige gas field in China. 44 horizontal wells have been tested achieving a great success. Among them, the AFO of 6 horizontal wells of G* well cluster is over one million m3, making the highest record in the horizontal well development history! So this set of seismic technology is an effective way to optimize the fracturing scheme of horizontal well in tight sandstone gas reservoir. Presentation Date: Tuesday, October 13, 2020 Session Start Time: 8:30 AM Presentation Time: 11:00 AM Location: 362D Presentation Type: Oral
Wang, Xianwen (Changqing Oil Company) | Fei, Shixiang (Changqing Oil Company) | Zhu, Lian (Changqing Oil Company) | Liu, Yuan (Schlumuberger) | Li, Haoyan (Schlumuberger) | Fu, Yunlong (Schlumuberger) | Wang, Weikan (Schlumuberger) | Wang, Lizhi (Schlumuberger)
For tight or unconventional reservoirs, multistage horizontal well fracturing and completion are necessary and important parts of the development. Previous studies have demonstrated that an engineered completion design improves lateral coverage and productive reservoir performance as compared with purely geometric designs. Because engineered completion design focuses on completion aspects, we introduce the idea and a case study of using geology quality (GQ) to improve multistage fracturing design in horizontal laterals. Reservoir Quality (RQ) and Completion Quality (CQ) are often based on formation evaluation result, capturing lithology, porosity, resistivity, or geomechanical properties only a few inches or feet from the wellbore. However, hydraulic fractures penetrate tens to hundreds of feet vertically and hundreds of feet horizontally. Therefore, geological factors must be considered to account for reservoir variability on a larger scale.
There are logical engineering reasons to vary the fracturing design along the lateral between stages. For a lateral that lands in the target reservoir, the fracturing design should be based not only on average reservoir properties but also reservoir height. For a lateral that lands above or below the target reservoir, special considerations must be taken to evaluate the chance that fractures will propagate into the target reservoir.
In our work, we convert this geology consideration quantitatively into a geology quality (GQ) number. This number reflects the reservoir effective height and relative distance from the wellbore, so that the fracturing design can be optimized in each stage along a horizontal lateral.
In a case study from Sulige Field, central China, we integrated GQ into six horizontal fracturing designs and operations with positive results. Breakdown issues were eliminated during the operation, and the production result satisfied expectations. Subsequent production analysis revealed the true contribution from different sand and shale sections in the lateral, enabling positive correlation to the GQ definition in the well. The addition of GQ to RQ and CQ has improved the science of optimizing fracturing design, completion staging, and perforation schemes.
Liu, Zhongneng (Oil & Gas Technology Research Institute of Changqing Oilfield Company, CNPC) | Wang, Zhiguo (National Engineering Laboratory for Exploration and Development of Low-Permeability Oil and Gas Fields) | Ren, Guofu (Oil & Gas Technology Research Institute of Changqing Oilfield Company, CNPC) | Guo, Siwen (National Engineering Laboratory for Exploration and Development of Low-Permeability Oil and Gas Fields) | Gui, Jie (Oil & Gas Technology Research Institute of Changqing Oilfield Company, CNPC) | Ren, Yong (National Engineering Laboratory for Exploration and Development of Low-Permeability Oil and Gas Fields) | Xue, Xiaowei (Oil & Gas Technology Research Institute of Changqing Oilfield Company, CNPC) | Zhao, Minqi (National Engineering Laboratory for Exploration and Development of Low-Permeability Oil and Gas Fields) | Feng, Changqing (Oil & Gas Technology Research Institute of Changqing Oilfield Company, CNPC)
Plugs have been widely used for staged fracturing in horizontal wells. But in wells with long lateral or low reservoir pressure, plug milling are far more complex due to debris accumulation and fluid loss. This study proposed a new multistage fracturing solution for horizontal wells using one kind of ball seat. Researchers have designed mechanical model of the seat. Metal material with great flexibility has been selected out and processed into seats according to the model. The key tools such as elastic seat, largediameter soluble ball and the matching tools such as cylinder and launching tool were developed. The results of indoor tests and large-scale simulation tests of real parameters have shown that the seat has the capability of repeated rebounding and the capacity of pressure bearing and packing reaches 70MPa. Field tests of 12 horizontal wells, containing totally 115 stages, have been carried out and achieved the technological goals of infinitely large-scale staged fracturing, no milling, and nearly full-bore access. The fracturing cycle has been shortened by more than 30% and the operation cost of single well has been reduced by more than 15%.
Zhao, Huawei (Sinopec Petroleum Exploration and Production Research Institute) | Zhao, Tianyi (Sinopec Petroleum Exploration and Production Research Institute) | Hou, Tengfei (CNPC Engineering Technology R&D Compnay Limited) | Lian, Peiqing (Sinopec Petroleum Exploration and Production Research Institute) | Shang, Xiaofei (Sinopec Petroleum Exploration and Production Research Institute) | Li, Meng (Sinopec Petroleum Exploration and Production Research Institute) | Zhang, Wenbiao (Sinopec Petroleum Exploration and Production Research Institute) | Wu, Shuang (Sinopec Petroleum Exploration and Production Research Institute) | Duan, Taizhong (Sinopec Petroleum Exploration and Production Research Institute)
Integrated characterization methods from micro-scale to macro-scale were applied to thoroughly study the petrophysical properties of the Upper Triassic Xujiahe fractured tight gas reservoirs. The lithology, pore types, pore structure, and porosity-permeability relationship were described based on experimental results of thin section analysis, computer tomography, and porometer and permeameter. And special attention was paid to characterize the natural fractures, and try to unveil the effects of fracture on gas storage and transportation. A dual-porosity dual-permeability (DPDP) dynamic model of well L150 was established, and the effects of natural fractures on the productivity were studied.
The lithology is mainly lithic arkose, feldsparthic litharenite, and litharenite. The formation is highly tight due to compaction and cementation during the early and middle burial stages, and only some interparticle pores and grain dissolution pores remained. Fractures are classified into two types, which are structural fractures and interlayer fractures. The first type is caused by tectonic movement, and is mainly developed in siltstone and fine sandstone; while the second type is developed between coarse sandstone beddings. Mercury injection capillary pressure experiment reveals that the pore size of the tight sandstone is 2-200 nm. The porosity of the samples is in the range of 2%-6%, and the permeability is 5 ×10-3-1×10-1 mD. Yet the permeability of some samples may be as large as 1000 mD because of the micro fractures. Results of history matching and production predictions of the dynamic model indicate that natural fracture is the important to natural gas production.