盐穴储气库茅23井“凸”形井眼井底注水泥塞技术

Bottom-hole cementing plug technology for convex well in Mao 23 well of salt cavern gas storage

茅23井是金坛盆地金坛凹陷直溪桥洼陷的一口盐穴储气库注采气定向井。二开中完钻时形成了上部井眼小、下部井眼大的“凸”字形井筒,加上由于在钻井过程中钻穿了盐层底板,导致试压不合格,需要对盐底以上进行注水泥塞封堵。分析了茅23井注水泥塞固井施工难点,优选饱和盐水前置液、抗盐水泥浆体系等固井液体系,配套采用“平衡法”注水泥塞、正注水泥反循环处理残浆固井工艺等技术措施,经过48 h候凝,实探塞面合格,试压30 min压降为0,水泥塞封固质量满足了盐穴储气库建设要求。

Well Mao 23 is one directional gas injection/production well of salt-cavern underground gas storage(UGS)in the Zhixiqiao subsag of Jintan Sag,the Jintan Basin.The convex shaped borehole which is small in the upper part and large in the lower part is formed during the completion of the second section.In addition,salt floor is penetrated in the process of drilling.As a result,the pressure test is not qualified.Therefore,it is necessary to adopt the cementing plug above the salt floor.The construction difficulties of cementing plug in Well Mao 23 were analyzed.Then,the cementing fluid systems were selected,e.g.the saturated saltwater prepad and the salt-resisting cement slurry system,and some technical measures were taken,including the“balanced”cementing plug and the cementing process of forward cementing and reverse circulating treatment of residual slurry.After 48 h wait on cement,the plug surface is tested to be qualified.After 30 min pressure test,the pressure drop is 0.Obviously,the cementing quality of the cement plug satisfies the construction requirements of salt-cavern UGS.