腰平1井钻井设计和施工难点分析

Drilling Design and Difficulties Analysis of well Yaoping 1

腰平1井是松南气田第一口火山岩气藏水平井,主要目的层为营城组。由于井眼轨道设计需考虑靶点垂深的不确定性和工具造斜率的不确定性,故选择了易于控制和调整的"直—增—稳—增—水平"五段制轨道类型。井身结构设计以简化结构、提高钻井速度为目的,具体为技术套管下至泉二段造斜点上部,并配套相关工艺技术。欠平衡设计时采取井筒环空循环介质循环当量密度略低于据储层孔隙压力折合的当量密度即可的思路,地层流体一定要有控制地流入井筒,同时还需考虑地层稳定性。针对大尺寸井眼防斜打直、火山岩地层可钻性差、多套地层护壁难度大等施工难点采取相应对策,取得了较好的施工效果。腰平1井钻井周期仅135.83d,比设计提前了15.1%;平均机械钻速2.60m/h,比同区块直井提高了6.7%;最大井斜为83°,实际井底水平位移868.90m,水平段长度480.61m。建议今后进一步开展东部地区提高深井大尺寸井眼钻井速度、火山岩气藏钻井方式等方面的深入研究。

The well Yaoping 1 is the first horizontal well in the volcanic rock gas reservoir of Songnan gasfield,whose intended zone is the Yingcheng formation.Based on considering the uncertainty of vertical depth of target spot and build-up rate by tools,＂straight-increment-stability-incremen-horizon＂ five-interval well trajectory is selected because of being easy to control and adjust.Well bore configuration should be simple and favorable for enhancing drilling rate.Intermediate casing will be run at upper deflection point in Quan 2 member,and matched technologies should be adopted.During the process of under balance design,cyclic equivalent density of the cyclic media in borehole annular should be a little less than the equivalent density gained by reservoir pore pressure,and formation fluid should flow into wellbore gradually so as to make the formation stable.Good application results have been achieved after corresponding countermeasures are taken according to the difficulties of large-dimension wellbore drilling,poor drillability of volcanic formations,sidewall prevention in many formations and so on.In well Yaoping 1,drilling cycle is only 135.83d,15.1% earlier than the design;average rate of penetration is 2.60m/h,enhanced by 6.7% than the straight well in the same block;and maximum well deviation is 83°,and actual downhole horizontal displacement is 868.90m and horizontal section length is 480.61m.It suggests that thorough research on enhancing drilling rate for deep large-dimension wellbore and drilling ways of the volcanic rock gas reservoir should be made further in eastern region in the future.