纳米复合泡沫凝胶修井液的研制与试验

随着油田水平井开发时间的延长，受储层物性及注采驱替系统难以建立等因素的影响，水平井部分开发区域地层压力保持水平较低，地层能量不足，修井作业过程中修井液漏失严重，作业循环建立困难，导致施工作业周期长、效率低等问题。依据泡沫流体特点，研发了一种强稳定性的纳米复合泡沫凝胶修井液，与常规活性水修井液相比，其稳定性高、密度低、降漏失性强，其主要配比为:1.4%起泡剂+0.25%纳米二氧化硅+0.5%聚合物+0.05%交联剂+0.02%稳定剂。该修井液体系主要以微泡作为分散相，凝胶为骨架，依靠泡沫的强承托能力和泡沫、凝胶的双层封堵特点，达到暂堵漏失地层、降低修井液漏失的目的。室内模拟实验表明，对于模拟岩心，初期体系滤失量几乎为零，稳定后漏失速率小于10 mL/min，显示出其良好的承压能力与降漏失特性。现场实验表明，该修井液性能稳定，能有效暂堵漏失层段、降漏失效果较好。研究表明，纳米复合泡沫凝胶修井液具有良好的暂堵降漏失效果，在低压水平井修井作业具有很好的应用前景。 

Development and Test of a Nanometer Compound Gel Foam Workover Fluid

Long time development of horizontal wells have their formation pressure and formation energy are gradually depleted because of the physical properties of the reservoirs and the difficulties setting up the injection-production displacement system. Depletion of reservoir pressure often results in severe mud losses during workover operations and reestablishment of circulation is generally quite difficult. These in turn result in long operation time and low operation efficiency. Based on the properties of foam fluid, a highly stable nanometer compound gel foam workover fluid has been developed to deal with this problem. Compared with conventional workover fluids formulated with active water, this foam workover fluid has higher stability, lower density and better capacity in preventing mud losses. The composition of the foam is as follows: 1.4% foaming agent + 0.25% nanometer SiO₂ + 0.5% polymer + 0.05% crosslinking agent + 0.02% stabilizer. This workover fluid uses micro foams as dispersed phase and gel as foam stabilizer, the loss of this workover fluid can be minimized by its strong retaining capacity and the combined ability of mud loss control of foam and gel which can help temporarily bridge the channels in the formations through which the workover fluid is lost. In laboratory simulation test, the initial fluid loss of the foam workover fluid through artificial cores was almost zero and the stable rate of loss was less than 10 mL/min, showing itself good pressure-bearing capacity and excellent performance of minimizing mud loss rate. Field test of the workover fluid showed that it had stable properties and was able to temporarily plug the loss zones. This study shows that the nanometer compound gel workover fluid has excellent temporary plugging capacity and ability of minimizing mud losses, it will find wide application in low-pressure horizontal well workover operations.