|Theme||Visible||Selectable||Appearance||Zoom Range (now: 0)|
Liwei, Wang (Research Institute of Petroleum Exploration & Development, Petro China) | Xiuling, Han (Research Institute of Petroleum Exploration & Development, Petro China) | Chunming, Xiong (Research Institute of Petroleum Exploration & Development, Petro China) | Bo, Wang (China university of petroleum) | Zhanwei, Yang (Research Institute of Petroleum Exploration & Development, Petro China) | Ying, Gao (Research Institute of Petroleum Exploration & Development, Petro China)
Volume fracturing and temporary blocking volume acid fracturing technology have been formed to improve stimulated reservoir volume in the Keshen gas field in China. The key factor for high yield is to make full use of the natural fractures in the reservoir. At present, the opening mechanism of natural fractures has been studied theoretically, but in combination with the temporary blocking process at the site, the indoor verification of different levels of natural fracture opening and coupling extension needs to be further strengthened.
The indoor physical experiment was carried out according to the outcrop rock sample 30cm×30cm×30cm. Three experimental schemes were designed to study the feasibility of temporarily blocking the natural fracture. The scheme is that the natural fractures are naturally closed without filling, the fracture aperture is less than 4mm, and more than 4mm.
Through the experiment, the following understandings are obtained: In the reservoir, not all fractures can open by temporarily blocking process. The fracture aperture is a very important factor. When the crack is no propped agent and naturally closed, the temporarily blocked powder forms a plug at the slit of the fracture, and the turn opens new fractures, but the opening pressure is high. In the first experiment, the maximum pump pressure was 19.11MPa, and the maximum pump pressure for the temporary blocking was as high as 39.757MPa. When the fracture aperture is less than 4mm, it is possible to temporarily turn the steering and open the new fracture. The maximum pumping pressure is 15.91MPa, and the maximum pumping pressure of the temporary plugging is as high as 27.29MPa;
According to the experiment, in the acid fracturing design, the process design and the temporary blocking material are optimized according to the grade of the reservoir fracture, which improves the design and optimizes the stimulation process.
At present, the Kuqa piedmont area in China's Tarim Oilfield is the main area of constructing a 30×108 gas zone in the oilfield (Yu Xiao, 2018) while Dabei and Keshen blocks are the main blocks in the Kuqa piedmont area. By the end of May 2019, more than 100 deep wells and ultra-deep wells had been successfully drilled in the Kuqa piedmont area, and 6 ultra-deep wells with their depths exceeding 8000 m had been drilled (Xu Haizhi, 2019). Natural fractures are well developed in the reservoirs. The thickness of stimulated layers is 100m-300m. The highest formation pressure coefficient reaches more than 2.0MPa/100m. It belongs to the ultra-deep fracture thick sandstone reservoir with high pressure and stress.
The Libra project is exploring and developing a very large deposit of oil and gas in the pre-salt area of Santos Basin, 100 miles offshore Brazil's coastline. Five companies have come together in a consortium together with Pré-sal Petróleo SA (PPSA) to develop this area under the country's first Production Sharing Contract (PSC). While still in the exploration phase, the project has been moving at a rapid pace, creating full field development scenarios, drilling wells, developing a system to collect dynamic reservoir information, and preparing for the initiation of its first production FPSO project. Ultimately, the field could see the drilling of nearly a hundred deepwater wells and the installation of several very large FPSOs. The area will be active with seismic, drilling, construction, production, installation and support vessels for many years.
By applying industry safety statistics to the large number of man-hours required to bring these plans to life, the potential for fatalities, Lost Time Accidents (LTI's) and other HSE incidences associated with the project can be statistically extrapolated. With these figures in mind, Project Leadership embarked upon a program to substantially improve safety performance with an objective to not only develop this rare field efficiently, but to establish a legacy of exceptional HSE performance. Now three years into Libra's exploration and development, and already exceeding 20 million man-hours expended, this paper seeks to share the steps taken to improve the HSE Culture of the Libra team and the performance of its contractors and subcontractors. Examples of physical changes in specifications to improve process safety, and changes in leadership behavior will be cited. The paper will discuss the successes, challenges, and future opportunities, in the hope that broader discussion of these efforts will assist this project and the industry to achieve project objectives while assuring safe working environments.
Yang, Zhao (PetroChina) | Fenjin, Sun (PetroChina) | Bo, Wang (PetroChina) | Xianyue, Xiong (PetroChina) | Wuzhong, Li (PetroChina) | Lianzhu, Cong (PetroChina) | Jiaosheng, Yang (PetroChina) | Meizhu, Wang (PetroChina)
Compared with the conventional oil and gas reservoirs, hydrogeological gas controlling process linking CBM accumulation, enrichment and high yield is one of the important scientific problems for the development of a CBM field. Previous research results are mainly focused on the impact of hydrodynamics on CBM dissipation, preservation and enrichment, whereas relatively less work has been done on the quantitative evaluation of the hydrochemical field of CBM and establishing evaluation indicators of CBM enrichment. Therefore, taking BQ Well area of Hancheng block in east Ordos Basin as an example, this paper tried to initiate a systematic analysis of the controlling function of hydrogeological conditions on the enrichment and high yield of CBM in the study area. Hydrological evaluation indicators for hydrocarbon enrichment zones are established and two favorable hydrocarbon enrichment zones are optimized. It is of great significance for the established analytical method of hydrogeological rule on the studies of CBM enrichment characteristics and development in Hancheng CBM block, and subsequent exploration & development in the neighboring blocks.
Firstly, the relevant principle of hydrodynamics is applied to identify substantive parameters, such as measured in-situ reservoir pressure and CBM reservoir water level in the production wells to calculate the reduced water level and analyze groundwater level distribution characteristics; secondly, combined with the analysis of groundwater water types, the sources of the produced water from coal beds are identified, and the sealing property of the reservoir is demonstrated; on this basis, the study area is divided into the weak runoff zone and the stagnation zone. It is considered that the runoff intensity is relatively weak and the sealing capability is good in the study area, with no external water intrusion; finally, it is considered that, through integrated studies on the hydrochemical field, the desulfuration coefficient and sodium chloride coefficient can reflect the diversity of CBM reservoir conditions in a more elaborated way. Hydrological indicators based on hydrochemical characteristics are established, and two favorable enrichment zones are predicted.
This work proved that hydrogeological features of CBM reservoirs are able to characterize their accumulation conditions elaborately. In particular, the establishment of hydrological indicators can classify favorable enrichment zones and hereafter guide following CBM exploration & development. This methodology has been satisfactorily applied in BQ well area of Hancheng block where the data of gas bearing capacity is limited. High single well production rates have been obtained in the two predicted favorable enrichment zones. The hydrological indicators established in this paper are expected to be popularized and applied in other well areas of Hancheng block, which may accelerate the overall exploration & development progress in this block.