大牛地气田水平段钻遇泥岩遇阻原因分析及对策

大牛地气田储层为低渗透砂岩储层,非均质性强.在盒1段水平井段的施工过程中,经常钻遇硬脆性泥岩,砂泥岩同层的复杂性导致遇阻情况频繁发生,严重影响了钻井指标及后期作业.为了防止或减少遇阻,结合实际生产情况对盒1储层水平段遇阻情况进行了全面分析,得出钻井液密度不合理、滤失量过大和钻井液携岩能力差是导致遇阻的主要原因.钻井液密度、流变参数以及环空返速都存在一个最优区间使遇阻程度最低;封堵孔隙和裂缝可较好的减少遏阻.提出适合钻穿泥岩段的钻井液性能及处理措施.

Encountering Resistance Mechanism and Countermeasures When Shale is Drilled in Horizontal Section of Daniudi Gasfield

The reservoir of Daniudi gas field is a low permeability sandstone reservoir, which is featured with strong heterogeneity. Hard brittle shale is drilled frequently in horizontal section of the he 1 member. Encountering resist- ance is often occurred due to the complexity of the sand and hard brittle shale in the same layer, which seriously af- fect the drilling index and late workings. For preventing or reducing encountering resistance, based on the practical production, encountering resistance in horizontal section of the he 1 member is analysed completely. Analysis shows that the unreasonable drilling fluid density, excessive filtration and low carrying cutting capacity are the main rea- sons which cause encountering resistance Drilling fluid density, rheological parameters and annular velocity all have the optimum interval in which encountering resistance occur - red rarely. Plugging pores and fractures can re- duce encountering resistance well. Drilling fluid property, treatment measures and corresponding engineering tech- nology measures which are suitable drilled mudstone section are put forward in this paper.