涠西南地区岩石特性及钻井液技术研究

Rock characteristics and drilling fluid technology in the Weixinan area

摘要:

北部湾盆地涠西南油田群是南海西部重要的原油产区，同时油田群紧邻众多国家级自然保护区，属于环境敏感区域。针对北部湾盆地涠西南地区环保要求，以及涠洲组和流沙港组钻井过程经常出现井壁失稳导致的憋卡、起下钻阻卡等问题，开展了涠西南地区地层泥页岩特性及环保钻井液技术研究。通过地层岩石黏土矿物分析、孔喉结构分析以及理化性能评价，明确了涠西南地区泥页岩井壁失稳的机理；提出以类油基的水溶性复合基基液为核心，构建了一套具有油基钻井液工程特性和水基钻井液环保特性的新型环保防塌钻井液技术，并进行了相关的现场应用。现场应用显示：应用井与邻井相比，12-1/4″井段阻卡划眼时间减少，井径扩大率大幅度降低，并且在128 h的长时间浸泡过程中没有复杂情况产生，有效地解决了涠洲组、流沙港组易失稳地层的井壁稳定问题；同时，钻井液环保性能达到一级海域环保要求，可以替代目前应用的油基钻井液体系，解决了海上使用油基钻井液存在配制成本高、含油钻屑需全回收及环境危害隐患大等技术难题。该研究对于涠西南油田环保、井壁失稳和钻井液技术发展具有较高的理论价值和借鉴意义。

Abstract:

The Weixinan oilfield group in the Beibu Gulf Basin is an important crude oil producing area in the western South China Sea. In addition, the oilfield group is adjacent to numerous national nature reserves and belongs to an environmentally sensitive area. In response to the environmental protection requirements of the southwestern region of the Beibu Gulf Basin, as well as the frequent problems of wellbore instability caused by blockage and tripping resistance during the drilling process of the Weizhou and Liushagang Formations, this study analyzed. the characteristics of shale and environmentally friendly drilling fluid technology in the Weixinan area. The mechanism of shale wellbore instability in the Weixinan area was determined through analysis of clay minerals in strata, pore throat structures, and physicochemical performance evaluation. A new environmentally friendly anti collapse drilling fluid technology with oil-based water-soluble composite base fluid as the core has been proposed, which has the engineering characteristics of oil-based drilling fluid and the environmental protection characteristics of water-based drilling fluid. Relevant on-site applications have been carried out. On-site application shows that compared with adjacent wells, the 12-1/4 "well section has a reduced time for sticking and reaming, a significant reduction in wellbore enlargement rate, and no complex situations occur during the long -term immersion process of 128 hours. This effectively solves the problem of wellbore stability in unstable formations of the Weizhou Formation and Liushagang Formation. The environmental protection performance of drilling fluid meets the first level marine environmental protection requirements, which can replace the currently used oil-based dilling fluid system and solve the technical problems of high preparation cost, full recovery of oily dilling cuttings, and high environmental hazards in offshore use of oil-based drilling fluid. The research results have high theoretical value and reference significance for the environmental protection, wellbore instability, and drlling fluid technology development of Weixinan oilfeld.