湖南复杂地质条件区页岩气勘探优快钻井技术

Research on optimized and fast drilling technology for shale gas exploration in complex geological condition areas of Hunan

摘要:

湖南省页岩气资源潜力巨大，但受扬子陆块与江南隆起推覆带复合构造控制，区内褶皱断裂发育、岩溶广泛分布、泥页岩水敏性强且软硬互层频繁，导致深井钻探中井漏、井塌、井斜、取心困难、固井质量差及井控风险高等工程问题频发，严重制约勘探开发进程。本文依据湖南省境内的60余口页岩气井资料和湖南省煤炭地质勘查院实施的30余口页岩气钻井的施工实践与重点井现场试验，系统分析了湘西北及湘中南地区寒武系牛蹄塘组、志留系龙马溪组、石炭系测水组、二叠系龙潭组及泥盆系佘田桥组5套主力含气层系的工程地质特征与关键工程难题。针对页岩气井关键工程难题，研发了低密度膨胀型承压堵漏技术（实现长段多漏点一次性封堵）、构建了“强抑制+高效封堵”一体化防塌技术体系（热滚回收率≥99.6%、16 h膨胀率≤3.24%）、研制了三种新型绳索取心钻具（岩心收获率由70%提升至90%以上）、形成了PDC钻头+单弯螺杆+MWD/LWD井眼轨迹精准控制技术、建立了“近平衡钻进—主动节流排气—坐岗预警”一体化井控技术体系，以及“安全下入—高效顶替—高韧性防窜”成套固井技术（固井优质率达100%）最终形成了适用于湖南省复杂地质条件区的四开次分段钻进、钻井液分级维护、固井全过程质控的页岩气井钻探施工技术体系，已在30余口井中成功应用，为南方复杂地质区页岩气及其他深部矿产钻探提供了重要技术支撑。

Abstract:

Hunan Province has huge potential of shale gas resources， however， controlled by the composite structure of the Yangtze Block and the Jiangnan Uplift Nappe Belt， well-developed folds and faults， extensive karst distribution， strong water sensitivity of shale formations， and frequent interbedding of hard and soft rocks are characterized in this area， leading to frequent engineering problems in deep drilling， such as lost circulation， borehole collapse， well deviation， difficult coring， poor cementing quality， and high well control risks， which severely restrict the exploration and development process. Based on data from more than 60 shale gas wells in Hunan Province， as well as the drilling practice and field tests of key wells from more than 30 shale gas wells implemented by the Hunan Coal Geological Exploration Institute， this paper systematically analyzes the engineering geological characteristics and key engineering challenges of five major gas-bearing formations in northwestern and central-southern Hunan， namely the Niutitang Formation of the Cambrian， the Longmaxi Formation of the Silurian， the Ceshui Formation of the Carboniferous， the Longtan Formation of the Permian， and the Shetianqiao Formation of the Devonian. To address the key engineering challenges of shale gas wells， a low-density expandable pressure-bearing lost circulation control technology has been developed （achieving one-time sealing of long sections with multiple loss zones）； an integrated anti-sloughing technology system of "strong inhibition+high-efficiency sealing" has been established （achieving a hot-rolling recovery rate of more than 99.6% and a 16 h expansion rate of no larger than 3.24%）； three new types of wire-line coring tools have been developed （increasing the core recovery rate from about 70% to over 90%）； a precise wellbore trajectory control technology combining PDC bit， single-bend screw motor and MWD/LWD has been developed； an integrated well control technology system of "near-balanced drilling-active throttling circulation-mud logging warning" has been established； and a complete set of cementing technologies featuring "safe casing running-high efficiency displacement-high toughness anti-channeling" has been formed （achieving a 100% high quality cementing rate）. Finally， a deep shale gas drilling construction technology system suitable for the complex geological conditions of Hunan Province has been developed， consisting of four-spud sectional drilling， graded drilling fluid maintenance， and whole-process quality control of cementing. This system has been successfully applied in more than 30 wells， providing important technical support for shale gas and other deep mineral exploration in complex geological areas of South China.