共和盆地干热岩GH-05井钻井关键技术

Key technologies of Well GH-05 drilling for hot dry rock in Gonghe Basin

摘要:

GH-05井是青海共和盆地干热岩试采工程部署的一口增效井，设计井深4000 m，为双靶点定向井。在邻井施工经验基础上，增加了表层套管与技术套管下入深度，降低了长裸眼段掉块卡钻风险，提高了生产套管固井质量。钻具组合增加减震推力器与随钻震击器，有效降低了剧烈震动对井下工具的不良影响，马达寿命提高35%，未出现牙轮脱落、轴承失效、断钻具等事故，及时处理了刮卡，实现了安全钻进。基于岩石破碎比能理论，兼顾碎岩效率和牙轮寿命，满足岩屑上返的需要，?311.2 mm口径选择钻压203~291 kN、转速120~180 r/min、泵量43.3~51.4 L/s，?215.9 mm口径选择钻压131~186 kN、转速180~270 r/min、泵量33~38.5 L/s，强化钻井参数使花岗岩地层机械钻速提高了34%~47%，钻井周期缩短了20%以上，创造了?311.2 mm钻头207.51 m和?215.9 mm钻头183.42 m的花岗岩钻进纪录，基本实现“机械钻速4 m/h、钻头寿命200 m”的经济指标。研发并应用耐温220 ℃复合有机盐钻井液体系，降低了热储层近井污染，有效降低定向托压，泥浆维护成本降低40%以上。

Abstract:

Well GH-05 is an efficiency-enhancing well deployed for the hot dry rock pilot production project in the Gonghe Basin， Qinghai Province. It is a dual-target directional well with a designed depth of 4000 m. Based on the construction experience of adjacent wells， the running depth of the surface casing and technical casing was increased， the risk of block falling and sticking in the long open hole section was reduced， and the cementing quality of the production casing was improved. In addition， a shock-absorbing thruster and a drilling jar were added in the bottom hole assembly， which effectively reduced the adverse effects of severe vibrations on downhole tools. The service life of the motor was increased by 35%， and no accidents happened such as cone dropout， bearing failure， and drill string breakage， achieving safe drilling. Based on the theory of specific energy of rock fragmentation， taking both the rock fragmentation efficiency and roller cone bit life into account， meeting the upward return of cuttings， for the borehole diameter of ?311.2 and ?215.9 mm， the weights on bit were selected to be 203~291 and 131~186 kN respectively， the rotational speeds were 120~180 and 180~270 r/min respectively， and the displacements were 43.3~51.4 and 33~38.5 L/s respectively. Furthermore， strengthening the drilling parameters increased the rate of penetration （ROP） in the granite formation by 34%~47%， and the drilling cycle was shortened by over 20%. It has created the drilling records of 207.51 m with a ?311.2 mm bit and 183.42 m with a ?215.9 mm bit in the granite formation， basically achieving the economic indicators of “ROP of 4 m/h and bit life of 200 m”. Finally， a composite organic salt drilling fluid system with a temperature resistance of 220 °C was developed and applied， reducing the near-wellbore pollution in the geothermal reservoir， effectively reducing the directional sticking pressure， and cutting the drilling fluid maintenance costs by over 40%.