摘要
南堡3号构造东二段以下地层在钻井过程中频繁发生井壁失稳现象。通过黏土矿物分析、FMI成像测井、电镜扫描、浸泡及CT扫描分析可知,中深层泥岩微裂缝发育,在钻井压差作用下,微裂缝发生自吸水效应,一方面使得近井壁的孔隙压力升高,另一方面,地层发生水化作用,由于岩石的受力不均使得微裂缝进一步开启;同时流体压力产生的尖劈效应会导致近井壁岩石的崩落和掉块,甚至井塌与井漏相互作用及影响。实验结果表明,井壁稳定技术的关键是对裂缝的封堵,使用了3%高软化点的抗高温封堵剂FT3000,以及SPNH、SMP和0.8%增黏降滤失剂DSP。形成的KCl抗高温封堵钻井液具有较好的封堵性能,可以形成致密的泥饼,渗透失水、砂床失水均较低,回收率大于90%,可以满足现场要求。该钻井液在现场应用后,井眼质量得到有效改善,井径规则,复杂事故率低,钻井周期从2012年开发初期的119.25 d缩短至目前的46.4 d,机械钻速从最初的6.65 m/s提高到12.05 m/s,提速效果显著。
Borehole instability has been taking place in drilling the Dong-Er member of the No. 3 Structure in Nanpu. It is found that micro-fractures are quite developed in the deep shale formations, which, under differential pressures, causes water imbibition into the fractures. The absorbed water increases pore pressure of the formations and causes formation to hydrate. Un-uniformity of forces developed in the formations as a result of hydration further enlarges the opening of fractures. Edgetone effect of pressures exerted by drilling fluid causes formation rocks near the borehole wall to slough. Laboratory experiments show that the key to the success of borehole stabilization is to plug and sealthe fractures. A KCl drilling fluid is formulated with 3% FT3000, a plugging agentwithhigh softening point, SPNH, SMP, and 0.8% DSP, a filter loss reducer having viscosifying effect. This drilling fluid has superior plugging and sealing performance as shown in laboratory experiments. In field applications, borehole collapse has been remarkably minimized, and drilling time is reduced from 119.25 d in 2012 to the present 46.4 d, and ROP increased from 6.65 m/s to 12.05 m/s.
出处
《钻井液与完井液》
CAS
北大核心
2015年第5期41-45,103-104,共5页
Drilling Fluid & Completion Fluid
关键词
井壁稳定
硬脆性泥岩
强封堵钻井液
南堡油田
Borehole stabilization
Hard and brittle shale
Plugging and sealing drilling fluid
Nanpu oilfield
