Formation damage control of saline-lacustrine fractured tight oil reservoir during well drilling
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ORIGINAL PAPER
Formation damage control of saline-lacustrine fractured tight oil reservoir during well drilling Xiwen Zhang 1 & Lijun You 2 & Yili Kang 2 & Chuang Zhang 3 & Guohui Zhang 1 & Qigui Tan 2 Received: 26 May 2020 / Accepted: 6 October 2020 # Saudi Society for Geosciences 2020
Abstract Formation damage is commonly known as a great cause for the production decline, owing to the unclear formation damage mechanisms under the reservoir geological and engineering conditions. This paper aims to develop a formation damage control technology during drilling for the protection of the natural productivity of saline-lacustrine reservoir. Reservoir geological characterization is first presented, including formation mineralogy, petrophysical properties, and fracture developing features. Fluid and stress sensitivity and in situ drilling fluid damage are experimentally evaluated under the simulated reservoir conditions. Successively, formation damage mechanisms during drilling are comprehensively summarized based on the evaluation results. It is believed that lost circulation is the main reason for formation damage, which further induce other damage. Given the formation damage mechanisms, principles of formation damage control technology for saline-lacustrine carbonate reservoir are explored, and in situ drilling fluids are optimized. The optimized drilling fluids are validated by lab experiments and field trials in Qaidam Basin. Field trials indicate that daily decline rate of productivity is decreased and per-well daily yield is increased by 7.7% year-on-year by using the optimized drilling fluids. This work could provide an effective guideline of formation damage control for saline-lacustrine reservoirs. Keywords Formation damage . Production decline . Saline lacustrine . Carbonate reservoir . Stress sensitivity . Drilling fluids
Introduction Recently, unconventional resources have increasingly gained more and more popularity from exploration and development to guarantee the daily increasing demand of energy and the orderly operation of industries (Ling et al. 2015). As a result, formation damage, occurring during the hydrocarbon development from the unconventional reservoirs in corresponding Responsible Editor: Santanu Banerjee * Lijun You [email protected] * Qigui Tan [email protected] 1
Research Institute of CNPC Petroleum Exploration and Development, Beijing 100083, China
2
State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, Sichuan Province, China
3
PetroChina Qinghai Oilfield Company, Dunhuang 736202, Gansu Province, China
operations including drilling, completion, production, hydraulic fracturing, and workover operations, becomes a hot topic these days (Bennion 2002; Civan 2007; Xu et al. 2016). Formation damage is technically designed as a cause for the undesirable reduction of permeability by the above process, and subsequently the productivity decline of oil and gas (Civan 2007), which is mainly caused by the four following mechani
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