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    Your Position :Home->Past Journals Catalog->2023 Vol.3

    Research on the stimulation technology for ultra-deep tuff reservoirs modification in northeast Sichuan
    Author of the article:LIU Hu1, ZUO Luo2,3, YIN Decan1, JIANG Tingxue2,3, DUAN Hua1, WANG Haitao2,3
    Author's Workplace:1. Sinopec Exploration Company, Chengdu, Sichuan, 610041, China; 2. State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development, Beijing, 102206, China; 3. Sinopec Research Institute of Petroleum Engineering Co., Ltd., Beijing, 102206, China
    Key Words:Ultra-deep;Tuff; Acidification; Acid fracturing; Carbon dioxide
    Abstract:

     Reservoir stimulation technology of horizontal wells in ultra-deep tuff reservoirs in northeastern Sichuan is not well established, then, analyzing geological characteristics, testing of physical parameters and rock mechanics parameters, and the research on the characteristics of fracture initiation and expansion are carried out to explore its effect on reservoir stimulation. The study shows that the ultra-deep tuff reservoir in northeastern Sichuan is thin in thickness, and belongs to low porosity and low permeability reservoir, featuring high clay mineral content, low brittleness index, strong plasticity, and complex lithology in the vertical direction of stratum; the fracture pressure of the reservoir is above 170 MPa, the stress difference is greater than 20 MPa, the fracture initiation and expansion are difficult, and at the same time, it is easy to cause high pumping pressure; as stratum is easy to disperse and collapse after the action of the reservoir rock and the acid system, so staged acid fracturing completion mode with cementing slip casing is mostly needed, which all need to be equipped with 175 MPa fracturing wellhead and equipment to enhance pumping rate and fracturing effect; measures such as pre-padding liquid CO2 and low-viscosity liquid, using deep penetration with aperture perforation and high-temperature resistant heavier fracturing fluid can lower the fracturing pressure and pumping pressure; it is recommended to use 15% hydrochloric acid as the base liquid of the acid fluid system. The acid fluid system must meet the requirements of 160℃rheological test and 140℃dynamic corrosion and no weak crosslinking and viscosity increase after standing for 7 days, and viscosity reaches 40 mPa·s and above after shearing for 35 min, as well less residue, no precipitation and no agglomeration. The stimulation technology for reservoir modification proposed in this paper is important reference and guidance for the effective exploration and development of ultra-deep tuff reservoirs in northeast Sichuan in the future.

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