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Sinopec has announced that the Dongye Deep 2 key shale gas well in Dongxi, Chongqing, was drilled to a total depth of 4300 m and tested at 412000 m3/d of high-quality natural gas. The operator said the result shows significant progress in ultradeep shale gas exploration in China and will increase Sinopec's shale gas production capacity in southeast Sichuan by more than 2 trillion m3. Following the breakthrough of the Fuling shale gas field in 2012, Sinopec has been expanding its expertise in deep shale gas. In 2018, Sinopec discovered and commercialized the Weirong shale gas field at a depth of 3800 m. The technical requirements of developing deep marine shale gas reservoirs at depths exceeding 4000 m are high due to challenges faced at ultrahigh depths and complex crustal stress.
Jia, Min (PetroChina RIPED) | Zhang, Jianjun (PetroChina RIPED) | Han, Xiuling (PetroChina RIPED) | Shi, Junfeng (PetroChina RIPED) | Guo, Donghong (PetroChina RIPED) | Cao, Guangqiang (PetroChina RIPED) | Li, Jun (PetroChina RIPED) | Li, Nan (PetroChina RIPED) | Wang, Haoyu (PetroChina RIPED) | Zhang, Yi (PetroChina RIPED) | Liu, Yan (PetroChina RIPED)
Abstract Deliquification is the primary technique for stabilizing gas production and improving gas recovery in gas fields producing water, and foam deliquification is the key subject of research for the purpose of enhancing gas production and cutting down cost. However, there is no systematic method to evaluate and compare the effects of foam deliquification in gas wells in various conditions. Aiming at the above problem, a new fuzzy quantitative evaluation method for foam deliquification is proposed. The method focus on four indicators, namely, rate of change in daily gas production, rate of change in daily water production, rate of change in the difference between tubing and casing pressures, and rate of change in daily injection cost. The evaluation results are calculated by the linear analysis, hierarchy analysis and fuzzy relation synthesis operator. The method has been applied to 30 foam deliquification wells in Sulige gas field and Chongqing gas field, and the comprehensive index of foam deliquification effect is calculated. The advantage of this method is that the technical and economic factors affecting foam deliquifiction, the membership relationships of various indicators, as well as the weight coefficients of the indicators are integratedly considered. It can be used for comprehensive evaluation and quantitative comparison of foam deliquification effects in gas wells in various conditions, assisting in determining candidate wells for foam deliquification, and guiding the selection of foaming agents.
Sinopec announced this week that production at China's largest shale-gas development has jumped 20% year-over-year. This is based on first quarter results that showed natural-gas production from the Fuling gas field in Chongqing reached a cumulative output of 1.78 Bcm, or nearly 63 Bcf. The boost comes after Sinopec brought 28 new wells on stream this year, the state-owned oil and gas producer said in an announcement. Sinopec is China's second-largest gas producer and said during its earnings call that it is aiming for an annual increase in gas output of 10% over the next 3 years. The operator produced a total of 30.2 Bcm in 2020 and is aiming for 34 Bcm this year. Sinopec's next expected milestones are 38 Bcm in 2022 and 42 Bcm in 2023.
Wu, Jiwei (East China University of Science and Technology, Harvard University, Yangtze University) | Pan, Jiake (East China University of Science and Technology) | Wang, Hualin (East China University of Science and Technology (Corresponding author) | Wang, Lixiang (email: email@example.com)) | Liu, Wenjin (PetroChina Southwest Oil & Gas Field Company, Chengdu Natural Gas Chemical General Plant) | Zhang, Le (Sinopec, SJ Petroleum Machinery)
Summary With the flourishing shale gas exploitation producing more oil-based mud (OBM) cuttings, the hard-to-treat hazardous wastes heavily burden the local environment. However, the problems of treating OBM cuttings, such as huge energy consumption, tremendous treatment costs, and high risk of secondary contamination, still remain unsolved with the current treatment technologies, such as thermal desorption, incineration, and chemical extraction. In this study, we introduce a new method and equipment based on cyclone desorption to recover oil from OBM cuttings. The technological process includes viscosity reduction in heated gas, cyclone deoiling, condensation and recycling of the exhaust, and separation of oil and water in the coalescer. Based on the analysis of the physicochemical properties and the oil distribution inside the OBM cuttings samples collected from the Chongqing shale gas field, we designed this cyclone oil desorption technology and built the pilot-scale equipment to conduct the deoiling experiments. The results showed that the deoiling efficiency of OBM cuttings improved as the processing time increased. To be precise, after 2.7 seconds of treatment, the oil content of the cuttings samples fell sharply from 17.9 to 0.16%, which is about one-half of the maximum allowable oil content in pollutants of 0.3%, specified in the national standard (GB 4284-84 1985) promulgated by the People’s Republic of China. The foundation of the technology is that the particles have a high-speedself-rotation (more than 30,000 rad/s) coupled with a revolution in the cyclone in which a generated centrifugal force removes the oil from the pores of the particles. This process is purely physical and involves no phase change of the oil, so it is free of chemical addition and high heating temperature. The application of this newly developed cyclone oil desorption technology is expected to lower the treatment costs, enhance the processing efficiency, contribute to the energy development, and eventually benefit the local environment where the shale gas exploitations take place.
Sinopec recorded China's highest daily output of shale gas at 20.62 million cubic meters (Mcm) at its Fuling shale-gas field in Chongqing, China, a key gas source for the Sichuan-East gas pipeline. The first major commercial shale-gas project in China, Fuling has continuously broken records for the shortest gasfield drilling cycle while significantly increasing the drilling of high-quality reservoirs covering more than 3 million m, according to Sinopec. Gasfield production construction was also expanded to raise production capacity. The company said the field maintains a daily output of 20 Mcm, producing an estimated 6.7 Bcm per year.
The Pugang gas field, one of the biggest inland gas discoveries of the last decade in China, has hydrogen sulfide (H2S) concentrations as high as 10%, making surface- and downhole-facilities design and execution challenging. Testing these wells also is difficult because of the surface risks inherent in conventional testing. Well testing using production-logging tools recently has been introduced in this field and has been of tremendous benefit to the operator in identifying the inflow zones and in performing well-test analysis. The Pugang gas field, discovered in 2002, is the second-largest gas field in China and the largest sour field discovered in the last decade. This field is north of Chongqing in the Sichuan basin.
Zhang, Xin (College of Petroleum Engineering / China University of Petroleum) | Li, Jun (College of Petroleum Engineering / China University of Petroleum) | Liu, Gonghui (College of Petroleum Engineering / China University of Petroleum) | Zhao, Chaojie (College of Petroleum Engineering / China University of Petroleum) | Yao, Yong (Sinopec Southwest Petroleum Engineering Co., Ltd.) | Jiao, Jianfang (Sinopec Southwest Petroleum Engineering Co., Ltd.)
ABSTRACT: Casing deformation in shale gas wells during multi-fracturing has seriously affected the efficiency and safety of shale gas production in China. Firstly, the characteristics of casing deformation in Weiyuan shale gas field were statistically analyzed, and main influence factors were obtained. Second, the influence of the induced stress from crack is analyzed, and a stress analysis model for casing-cement-formation system stress field nearby wellbore during fracturing is established. Finally, the loads near wellbore in shale gas wells is studied, incorporating variation fracturing methods and operation parameters. The results show that the casing deformation in shale gas wells mainly occurs near the heel of the horizontal section, and shear failure is the main type of casing deformation; The initiation and expansion of crack can lead to the accumulation of non-uniform stress nearby wellbore during fracturing. Further, this will induce formation slip and cause the shear and collapse failure of casing; Accurate identification of faults, natural cracks and improved fracturing technology can alleviate the stress concentration of the casing and reduce the risk of casing deformation failure. This study further reveals the mechanism of casing deformation during multi-fracturing in shale gas wells, and proposes fracturing measures for casing integrity. The results demonstrated in this paper can provide the theoretical basis for preventing casing deformation during fracturing in shale gas wells. 1. INTRODUCTION With the development of unconventional gas reservoirs for shale gas in the world, Significant progress in the exploration and development of shale gas has been made in China recent years, including the construction of the Changning-Weiyuan shale gas field of CNPC and the Chongqing Fuling shale gas field of Sinopec. However, in the national shale gas demonstration area of the Changning-Weiyuan, southwestern Sichuan Basin, since the exploration and development in 2013, some shale gas wells have had some problems, such as poor cementing seal integrity and serious casing deformation. Difficulties in the entry of casings in horizontal well sections, especially in the process of fracturing stimulation and transformation, the impact of casing deformation on the smooth entry of bridge plugs has caused some reservoir sections to be forced to abandon, and even the bridge plugs cannot be drilled smoothly. The emergence of these problems has affected the improvement of single well production in shale gas horizontal wells.
Wu, Jiwei (East China University of Science and Technology, Yangtze University) | Pan, Jiake (East China University of Science and Technology) | Wang, Hualin (East China University of Science and Technology) | Wang, Lixiang (PetroChina Southwest Oil & Gas Field Company Chengdu Natural Gas Chemical General Plant) | Lan, Xiaoping (PetroChina Southwest Oil & Gas Field Company Chengdu Natural Gas Chemical General Plant) | Yang, Lijie (PetroChina Southwest Oil & Gas Field Company Chengdu Natural Gas Chemical General Plant) | Liu, Wenjin (SJ Petroleum Machinery CO.SINOPEC)
With the flourishing shale gas exploitation produces more oil based mud (OBM) drill cuttings, the hard-to-treat hazardous waste burden the local environment heavily. However, the problems of high energy consumption, high treating cost and high secondary contamination risk still remain unsolved for mainstream technologies such as thermal distillation, incineration and chemical extraction. Therefore, a new method and device based on cyclone desorption of high speed self-rotation to dispose of OBM drill cuttings are put forward to overcome the challenge. The working process includes: viscosity reduction in heated gas; cyclone deoiling; condensation and recycling of exhaust; separation of oil and water in coalescer. It is found that the self-rotation speed of solid particles in a 3-dimensional rotating turbulent flow field of cyclone is as high as 2,000 to 6,000 rad/s which coexists with revolution speed of 20 to 300 rpm. The remarkable pulsing centrifuge forces in the self-rotation and revolution coupling motion can enhance the desorption process of the oil so as to accomplish the separation and enrichment of oil and solid phase, and deep removal of organics from OBM drill cuttings. It turned out that the deoiling efficiency of OBM drill cuttings, a sample from Chongqing shale gas field, increased as the processing time longer and, to be exact, after 2.1 seconds the oil content fell from 17.9% to 0.16% which is about a half of the maximum allowable content of petroleum in pollutants, 0.3%, in GB 4284-84 "Control Standards for Pollutants in Agricultural Sludge". In general, the innovation of cyclone desorption of high speed self-rotation is the pulsing centrifuge force of self-rotation and revolution coupling motion, so it's free of chemical addition and high heating temperature. Therefore, the application of cyclone desorption of high speed self-rotation for OBM drill cuttings disposal is expected to lower treatment cost, enhance processing effect, and finally improve the environment of shale gas exploitation area and contribute to energy development.
Jiang, Long (China University of Petroleum, East China) | Cheng, Yuanfang (China University of Petroleum, East China) | Han, Zhongying (China University of Petroleum, East China) | Gao, Qi (China University of Petroleum, East China) | Yan, Chuanliang (China University of Petroleum, East China) | Wang, Guihua (China University of Petroleum, East China) | Wang, Huaidong (CCCC Marine Construction & Development Co., LTD) | Fu, Lipei (Changzhou University)
Abstract With the application of hydraulic fracturing in unconventional gas reservoirs, large-scale fracturing operations have resulted in water shortage and environmental pollution. Many scholars and governments gradually began to explore many waterless fracturing technologies in recent years, such as high-energy gas fracturing, liquefied petroleum gas fracturing, nitrogen foam fracturing, liquid/supercritical CO2 fracturing, and cryogenic fracturing using liquid nitrogen (LN2), etc. As a waterless fracturing technology, LN2 fracturing can significantly improve the coalbed methane and shale gas wells production, greatly improving the effectiveness of reservoir stimulation. But the efficiency mechanism and influencing factors of LN2 fracturing were still not clear in well bottom conditions. To investigate the influence of LN2 treatment on pore characteristics and carrying capacities of anisotropic shale, the shale from the Longmaxi formation in Chongqing, China, was selected as samples for LN2 treatment experiment. A series of permeability, ultrasonic wave, nuclear magnetic resonance (NMR) and triaxial compression experiments were conducted on different bedding shales. In pore structure tests, the increasing range of permeability is 8.01% – 74.36%, and the P-wave velocity decreases by 4.06% – 16.08%; in NMR tests, the morphology of transverse relaxation time (T2) distribution curves for LN2 treatment samples was significantly different than that of the original sample. Moreover, the change of the saturated sample is greater than that of the dry sample. In triaxial compression tests, the compressive strength, elastic modulus and brittleness of the shale were generally lower for all treated samples with LN2. The study results indicate that LN2 can cause serious irreversible damage to the internal structure of shale, which helps to open natural fractures and decrease the initiation pressure of reservoir stimulation. In cryogenic fracturing using LN2, it is of great significance to generate the complex fracture networks and improve the fracturing performance. This fracturing technology plays an important role in the development of unconventional natural gas with a bright future.
Zhu, Hai-Yan (Southwest Petroleum University) | Tao, Lei (Southwest Petroleum University) | Liu, Qing-You ((corresponding author), Southwest Petroleum University and Xihua University) | Lei, Zheng-Dong (RIPED, PetroChina) | Jiang, Shu (China University of Petroleum (East China) and University of Utah) | McLennan, John D. ((cocorresponding author) University of Utah)
Summary Currently, substantial shale gas reserves have been recognized in many countries, including China and the United States. An improved comprehension of the structure of these shale plays can lead to improved shale gas producibility. Gas is produced through natural fractures (NFs) and through hydraulically induced fractures, together creating the so-called stimulated reservoir volume (SRV). Although NFs are advocated as significantly influencing the size and shape of an SRV, the effects of NFs on fracturing and permeability changes are incomplete. This paper describes experimental studies performed on calcite-filled fractures from outcrops of Wufeng (O3w)-Longmaxi (S1l) shale. These samples are representative of Ordovician-Silurian productive shales in the Fuling Basin, near Chongqing City, China. Basic parameters, such as acoustic wave velocity, porosity, and permeability, were first measured on representative samples. Subsequently, permeability and acoustic emissions were measured during triaxial compression experiments through the post-peak domain. After these evaluations, the fracture modes and the fragment distribution were evaluated. In the measurements made, the natural calcite-filled macroscopic fractures reduced the confined compressive strength of these shale samples from 26 to 47%. Permeability is also affected. During the triaxial compression experiments, different NF orientations affected the overall permeability differently. We divided the collected samples into three groups. Group 1 samples had axial fractures (AFs). The gas permeability reduced from 0.70 to 0.12 md. When the sample was broken, permeability increased to 2.0 md, whereas the axial stress dropped to zero. Samples in Group 2 had transverse natural fractures (TFs). When new fractures were generated, permeability increased to greater than 0.70 md. Because samples in Group 3 had no obvious, natural macroscopic fractures (NFs), permeability was too low to measure before catastrophic failure during triaxial compression. When these samples did fail in compression, significant fractures formed, and permeability increased, resembling Group 2. There was a close relationship between the initial pattern of NFs and the subsequently generated fracture morphologies. For Group 1, the samples broke into several larger pieces along the original AFs. For Group 2, the samples broke into numerous small and relatively uniform pieces. For Group 3, the samples did not break completely, and the constituent fragments were nonuniform. Our results are helpful for understanding fracture-propagation mechanisms and the evolution of permeability under in-situ loading processes (long-term geologic loading, stress alteration during well construction and stimulation, and reservoir modification during depletion).