无机盐水基解卡液的研究及其在长5井的应用

Research on Inorganic Saltwater Spotting Fluid and Its Application in Well Chang-5

酒泉盆地长沙岭构造砂泥岩段长,存在高压盐水层,平均钻井液密度在1.98-2.02 g/cm3之间,压井过程中压差卡钻事故频繁发生,过去通常采用油基解卡液浸泡解卡,配方复杂且污染钻井液。通过对无机盐、加重剂、渗透剂的优选,开发了一种由无机盐和OT为主要成分的新型的水基解卡液,提高了解卡速度和成功率。该解卡液防塌性好,在长时间浸泡后不会造成井塌复杂,解卡后可配合降滤失剂和稀释剂混入钻井液中,进一步提高钻井液的防塌性。通过室内评价实验,该解卡液抗温能力在140℃以上。在解卡仪上测得解卡时间最短为85 min,而油基解卡液的解卡时间最短为100 min。该解卡液荧光级别低,不会对录测井造成影响。

The Chang Sha Ling Structure in Jiuquan Basin has thick sand and mud stones,and high pressure saltwater zones which can only be balanced with high mud density(1.98-2.02 g/cm3).Differential pipe sticking had been frequently encountered during well killing,and the stuck pipes were commonly freed with oil base spotting fluids in the past.The oil base spotting fluids were complex in composition and often caused mud contamination.By carefully selecting inorganic salts,weighting agent and penetrant,a new water base spotting fluid containing inorganic salts and OT,was developed.The freeing of stuck pipes become easy by using the new spotting fluid.Bore hole stability can be maintained by using this spotting fluid even after a long-term of exposure of the bore hole in the fluid.When such pipes are freed successfully,the spotting fluid can be mixed with drilling fluid after treatment with filtrate reducers and thinners.Lab evaluation showed that this spotting fluid can be used at temperatures above 140 ℃.The shortest time freeing the stuck pipes is 85 min,whereas this time can be 100 min if oil base spotting fluids are used.This spotting fluid has low fluorescence value and will have no effect on the interpretation of well logging.