深水窄密度窗口地层封堵承压钻井液技术

Drilling Fluid Technology for Plugging and Strengthening Formations with Narrow Mud Weight Windows in Deep Water Drilling

针对深水地层压实程度低、钻井液安全密度窗口窄、易导致井漏的技术难题,以烯类单体、大分子交联剂及层状结构硅酸盐矿物等为主要原料制备了柔性颗粒封堵剂,以此为基础构建了深水抗高温封堵承压水基钻井液。室内实验证明,柔性颗粒封堵剂韧性好,抗温达160℃,在10%盐水中性能稳定,对渗透性岩心、裂缝及砂床均具有良好的封堵效果,显著提高承压能力;构建的深水抗高温封堵承压钻井液160℃老化前后流变性能稳定,黏度和切力合适,4℃与25℃下的动切力比值小于1.35,具有显著的低温恒流变特性,封堵后岩心的渗透率接近于零,承压能力达11 MPa,抗膨润土粉及氯化钠污染的能力强,保护储层效果良好,岩心渗透率恢复率大于90%。该深水抗高温封堵承压水基钻井液在南海陵水区块进行了现场应用,提高了易漏地层的承压能力,承压能力提高6~11 MPa,确保了复杂井段的钻井安全。

Formations drilled in deep water drilling are generally poorly compacted and have narrow safe mud weight windows,and mud losses in drilling these formations hence occur frequently.To solve these problems,a flexible particle plugging agent was developed with vinyl monomers,a macromolecular crosslinking agent and a silicate mineral with layered structure.Laboratory experimental results show that this flexible particle plugging agent has good toughness,and functions normally at temperatures as high as 160℃.In 10%salt water,the plugging agent has stable characteristics and can effectively plug permeable cores,fractures and sand-bed,significantly increasing their pressure bearing capacity.A high temperature drilling fluid for deep water drilling was treated with this plugging agent,and its properties before and after aging at 160℃were stable.This drilling fluid has proper viscosity and gel strengths,and the ratio of the yield points at 4℃and 25℃is less than 1.35,indicating that the drilling fluid has constant rheology at low temperatures.Cores plugged with this drilling fluid have permeability that is near zero,and the pressure bearing capacity of the cores is 11 MPa.This drilling fluid has strong resistance to the contamination by clays and salt,and is of low damage to the permeability of reservoir formations;permeability recovery of plugged cores is at least 90%.The application of this drilling fluid in the Lingshui block in South China Sea effectively increased the pressure bearing capacity by 6-11 MPa,ensuring the safe drilling operation in the complex hole sections.