川西马井气田钻井复杂情况及治理对策

马井气田探明地质储量175.58×10^8m^3,可采储量80.54×10^8m^3,是川西地区主要的天然气开发区域。该区地质构造复杂,主要表现为成岩作用差,层间缝发育,层系间不整合接触,断层发育,地层承压能力差;纵向上泥岩较发育,各组岩性疏松,胶结差,钻井施工中复杂情况发生率较高,为73.7%（统计57口已完钻井）,其中,井漏占65%,卡钻占17%,井喷、井涌占9%,井壁垮塌占5%,地层出水占4%,从而导致钻井速度缓慢、施工周期延长。对此,提出如下治理对策：采用新的钻井工艺,引进清水强钻和微泡沫钻井技术;钻井中使用强抑制性高钙盐聚合物钻井液,并合理调整其密度大小;调整井身结构,在一个裸眼井段内不能有压力悬殊的地层存在,在揭开储层前,应适当提高钻井液密度。同时,应加强对该区地层出水原因及治理方法的研究工作。

Well Drilling Incidents and Countermeasures in Majing Gasfield,Western Sichuan

Majing Gasfield is a main exploitation area in the western Sichuan with 175.58×10^8m^3 of the proven geologic reserves and 80.54×10^8m^3 of the recoverable reserves.Geological structure in this area is complex：weak diagenesis,developed interbed fractures,uncomformable contact among layer system,developed fault and low amount of pressurization in the formations.Mudstones were developed well in the vertical with loose lithology and poor cementation.Incidents took place in 73.7% of 57 drilled wells,among them,the ratio of circulation loss,bit freezing,blowout and kick,wall collapse and water breakthrough was 65%,17%,9%, 5% and 4% respectively.They resulted in slow drilling speed and longer operation cycle.So,some countermeasures should be taken.New drilling technologies will be introduced including wash boring and micro-foam drilling.High-calcium salt polymer drill fluid with strong inhabit will be used in drilling,whose density should be adjusted according to the situation.Bore frame should be adjusted,that is to say,the pressure has few differences at one whole barefoot interval and density of the drill fluid should be big enough before drilling. Study should be made on the cause of water breakthrough and corresponding measures in this area.