适用于辽河致密油地层的高性能钻井液技术

根据辽河油田沈北区块致密油储层的特点,对该区块沙河街组四段灰色硬脆性泥页岩易水化膨胀、垮塌掉块等问题进行了研究。通过对致密油页岩进行黏土矿物分析、纳米CT扫描成像和SEM电镜扫描实验,确定了油页岩的黏土矿物含量、平均孔隙半径和微裂缝的发育情况。根据致密油页岩地层的特点,针对性地进行了纳米级封堵剂的复配实验,在此基础上构建了一套强封堵、强抑制和弱冲刷的高性能钻井液体系,该钻井液在泥页岩岩屑中的一次回收率为93%以上,三次回收率接近80%,渗透率降低超过50%。现场应用2口井,成功解决了油页岩地层水化坍塌、井壁失稳导致的划眼、卡钻等技术难题。2口井应用结果表明,"高黏度"和"高切力"高性能钻井液体系使用后,易垮塌地层未出现井壁坍塌,恶性事故得到了有效控制,事故复杂率下降17%,完井周期减少150 d,提速效果明显。

High Performance Drilling Fluid Technology for Tight Oil Formation Drilling in Liaohe Oilfield

This paper introduces the characteristics of the tight oil reservoirs in the Shenbei block of Liaohe Oilfield and the studies performed on the hydration, swelling, sloughing and cave-in of the hard and brittle shales in the member 4 of the Shahejie formation in the block. Using clay mineral analysis, nano CT scan imaging and SEM, the tight oil shale was studied and the clay mineral content, average pore radius and the development of micro-fissures of the tight oil shale was determined. Laboratory tests were conducted to optimize a special compound nano plugging agent based on the characteristics of the tight oil shales. A high-performance drilling fluid with high plugging capacity, high inhibitive capacity and low erosion to borehole wall was formulated through laboratory study. The primary percent recovery of shale cuttings tested with the drilling fluid formulated was 93%, and the tertiary percent recovery of shale cuttings tested with the drilling fluid formulated was near 80%. The percent reduction of permeability was more than 50%. Field application of the drilling fluid on two wells showed that this "high viscosity high gel strength" drilling fluid successfully resolved downhole troubles such as borehole wall sloughing and cave-in, reaming and back-reaming in shale sections and pipe sticking that were previously encountered. Occurrence of downhole troubles was reduced by 17%. Time for well completion was reduced by150 d, demonstrating the effectiveness of ROP enhancement of using the drilling fluid.