Fracture Stimulation in the First Joint-Appraisal Shale-Gas Project in China

Abstract

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 16762, ’Successful Fracture Stimulation in the First Joint-Appraisal Shale-Gas Project in China,’ by Liang Jin, Changlong Zhu, Yong Ouyang, Ming Zhou, Qingguang Qu, Fei Li, Roger Yuan, Chris Wu, Zhiyi Zhang, Yan Wang, and Fa Dwan, Shell China Exploration & Production; Sanjay Vitthal, Shell Canada; and Shiqian Wang, PetroChina Southwest, prepared for the 2013 International Petroleum Technology Conference, Beijing, 26-28 March. The paper has not been peer reviewed. This paper discusses fracture stimulation in the first joint-venture shale-gas project with foreign companies in China. The block is in Sichuan province, and the target zone is Longmaxi hot shale, a Silurian formation. Its matrix permeability is extremely low (100 to 300 nanodarcies), but it is rich in natural fractures. Hydraulic fracturing has been shown to be critical to enhancing production. A collaborative approach was applied to the completion of the shale gas wells during appraisal. Introduction Most of China’s proved shale-gas resources are in the Sichuan, Tarim, and Ordos basins. China’s technically recoverable shale-gas resources are estimated at 1,275 Tcf. The operator jointly appraised a shale-gas block in Sichuan with PetroChina. The project team needed to make several determinations in the early phase of the project, such as whether there is sufficient gas in the shale formation and whether the gas can be extracted at a high-enough (commercial) rate. From the production technologists’ perspective, the technical objectives of the early wells included the following: Test the ability of the Longmaxi hot-shale interval to be fractured under high formation pressure. Establish baseline fracture designs for the Longmaxi hotshale interval, at greater than 3500-m true vertical depth (TVD), and systematically evaluate the design parameters. Establish an effective multidisciplinary workflow. Gather fracture-stimulation-performance data and subsurface-pressure information. Determine the productivity of the gas from the appraisal wells to prove the presence of a shale-gas play. The joint-appraisal phase began in November 2010. While planning the drilling of deep wells to evaluate the Longmaxi formation, data were obtained from several shallow wells at a location close to the surface. Extensive laboratory tests were conducted to evaluate the geochemical properties of the rock. In addition, some rock-mechanics properties were measured. The drilling of the first well (Well A) began in December 2010, and hydraulic fracturing began once the well reached designed depth. To date, five wells have been drilled; two are vertical, and three are horizontal.