复合盐饱和盐水钻井液在利97井中的应用

利97井是胜利油田布署的一口钻探盐下油气藏的重点探井,共钻遇3套盐膏层,盐膏层总厚度达600m,其井段岩性主要为盐膏岩、膏泥岩、纯盐岩及红色、灰色泥岩。根据该井地质特点和施工要求,配制复合盐饱和盐水钻井液体系,并进行热稳定性和抗污染性实验,在该井三开井段(2850～3915m)应用,取得良好效果。有效抑制了泥岩段地层黏土矿物的水化膨胀,钻井过程中无掉块,起下钻顺利;盐膏层钻井过程中,用Na2SO4控制钻井液中Ca2+含量,很好地控制了钻井液流变性和滤失量,减少了采用纯碱控制Ca2+含量对钻井液流变性造成的不利影响;用饱和盐水钻井液控制Cl-的浓度,使其一直处于饱和状态,钻井液未对井壁溶蚀,电测解释井眼相对规则;三开钻进、电测、完井及取心都非常顺利(盐膏层取心2次),表明复合盐饱和盐水钻井液体系适合该区块的钻井施工,值得推广应用。

Application of Drilling Fluids of Saturated Composite Salt Water in Well Li97

Well Li 97 is one of the key exploratory wells in subsalt reservoir located in Shengli oilfield.Three sets of salt-gypsum beds were drilled in this well with the thickness of 600m and the lithology of salt-gypsum rocks,gypsum-mudstone,net salt rock and red and grey mudstones.According to the geological character- istics and operating demands in this well,a drilling fluid system--saturated composite salt water was prepared,and the experiments on temperature resistance and pollution prevention were made.Good results were achieved after it was applied in the interval of 2850-3915m in this well.Hydrating swell of the clay mineral in the mudstone interval was controlled effectively,which resulted in successful trip in drilling.In the drilling process of the salt-gypsum beds,Na2SO4 was used for controlling the content of Ca2＋ in the drilling fluid,and then the rheology behavior and filter loss of the drilling fluid.The drilling fluid of saturated salt water controlled the concentration of Cl- and made it at saturation state.Borehole wall was not corroded by the drilling fluid and wellbore was regular relatively by electric-log interpretation.The successful drilling,electric log,well completion and coring show that the drilling fluid of saturated composite salt water fit for the operation in this block ,which is worthy of popularizing and applying.