Lu, Cong (Southwest Petroleum University) | Li, Junfeng (Southwest Petroleum University) | Luo, Yang (SINOPEC Southwest Oil & Gas field Company) | Chen, Chi (Southwest Petroleum University) | Xiao, Yongjun (Sichuan Changning Gas Development Co. Ltd) | Liu, Wang (Sichuan Changning Gas Development Co. Ltd) | Lu, Hongguang (Huayou Group Company Oilfied Chemistry Company of Southwest) | Guo, Jianchun (Southwest Petroleum University)
Temporary plugging during fracturing operation has become an efficient method to create complex fracture network in tight reservoirs with natural fractures. Accurate prediction of network propagation process plays a critical role in the plugging and fracturing parameters optimization. In this paper, the interaction between one single hydraulic fracture within temporary plugging segment and multiple natural fractures was simulated using a complex fracture development model. A new opening criterion for NF penetrated by non-orthogonal HF already was implemented to identify the dominate propagation direction of HF under plugging condition. Fracture displacements and induced stress field were determined by the three dimensional displacement discontinuity method, and the Gauss-Jordan and Levenberg-Marquardt methods were combined to handle the coupling between rock mechanics and fluid flow numerically. Numerical results demonstrate that the opening and development of NF are mainly dominated by its approaching angle and relative location. For a certain NF crossed by HF within plugging segment, HF tends to propagate along the relative upper part when the approaching angle is less than 90°, otherwise the lower part will be easier to open. The farther interaction position is away from HF tip, the easier NF with approaching angle less than 30° or larger than 150° can be open, and the outcome will be opposite if the approaching angle is larger than 45° or less than 135°. Higher approaching angle and plugging strength is necessary for expanding the position scope of NF that can be opened around HF. Under the impact of plugging, fluid pressure in HF plummets at the beginning of NF opening and keeps decreasing until NF extending for a certain distance or encountering secondary NFs. Fluid pressure drop occurs mainly in the unturned NF, together with the width of unturned NF is significantly lower than that of turned NF and HF. Sensitivity analysis shows that the main factors, such as geometry, aperture profile, and fluid pressure distribution, affecting the network progress under temporary plugging condition are the horizontal differential stress, NF position, approaching angle, plugging time, and plugging segment length. The simulation results provide critical insight into complex fracture propagation progress under temporary plugging condition, which should serve as guidelines for welling choosing and plugging optimization in temporary plugging fracturing.
Wang, Yang (Halliburton) | Zheng, Guangjie (Halliburton) | Wood, Kevin (Halliburton) | Xiao, Yongjun (Sichuan Changning Gas Development Co. Ltd.) | Yang, Yang (Sichuan Changning Gas Development Co. Ltd.) | Zhao, Hao (Sichuan Changning Gas Development Co. Ltd.) | Miao, Yun (Sichuan Shengnuo Oil and Gas Engineering Technology Service Co. Ltd)
The Weiyuan-Changning shale gas play is one of the most prolific exploration and development targets in China. This paper discusses a case study from a southern Sichuan shale gas field, expanding on the challenges encountered during exploitation of this reservoir, such as complex stratigraphy. Solutions are proposed based on examples of successful microseismic data application, highlighting potential necessary considerations when making project design decisions in such complex geological zones, such as the southern Sichuan basin.
Located in the southern Sichuan basin at the intersection of two major anticlines, the primary pay zone within the Changning is the Longmaxi. Because hydraulic fracture stimulation in this complex stratigraphy can be technically challenging, determining the created fracture geometries is crucial to evaluating the effectiveness of a stimulation application. Downhole microseismic fracture mapping was identified early during the development of this play as a solution to understanding the mechanics and results of subsurface stimulation. This technology was used to evaluate the hydraulic fracturing of three Ning201 horizontal gas wells in the Longmaxi.
Microseismic data acquisition in the Changning shale proved to be successful, as microseisms were detected at distances in excess of 1800 m from the Ning201 fracture treatments. Based on these data, a large fault to the west of the treatment wells significantly influenced fracture geometry, though not to the extent expected. However, crosscutting minor natural fractures that were activated during injection might have led to casing failure in one of the wells. These fractures, particularly natural fractures running parallel to the direction of maximum principal stress, should be considered when making project design decisions in complex geological zones, such as the southern Sichuan basin.
This paper provides an integrated analysis of a Changning hydraulic fracturing project based on microseismic data, previous completions in the area, and new information. This knowledge can be applied to help optimize future development of the Changning.
Fu, Yongqiang (PetroChina SouthWest Oil & Gas Company) | Xiao, Yongjun (Petrochina Southwest Oil and Gasfield Company) | Chen, Yuanlin (Petrochina Southwest Oil and Gasfield Company) | Zeng, Lixin (Petrochina Southwest Oil and Gasfield Company)
The shale gas resource is rich in Sichuan Basin, it has a great potential of exploration, by the evaluation, the shale gas resources in the Cambrian and Silurian is equivalent to 1.5 to 2.5 times of the Sichuan Basin conventional gas resources. In order to speed up the process of the development of shale gas fields in China, and to identify the rich shale resources in Sichuan Basin, PetroChina carried out an active exploration and evaluation work, and established the first national shale exploration and development industry demonstration area in Sichuan Basin Weiyuan-Changning. In demonstration zone, Weiyuan Cambrian M shale is depth in the 2500-3500m, the depth of high gamma shale is 50-60m, the TOC content of 3.0-4.0%,