封堵评价用微裂缝岩心的模拟及模拟封堵实验

Simulation of Core with Micro Cracks Used in Plugging Evaluation and Plugging Simulation Experiment

摘要:

采用不同厚度的金属箔片和胶凝材料浇筑出了微裂缝岩心，配合高温高压失水仪外筒和泥浆杯，通过监测30 min内的漏失量，即可开展微裂缝岩心封堵评价实验，评价钻井液的封堵效果。通过微观观察法和流量计算法对制作的微裂缝的表面形态和开度进行了验证，结果表明岩心缝面具有一定的粗糙度，裂缝开度符合实验设计，最小3.33 μm，且岩心具有5～10 cm的裂缝行程。微裂缝岩心制作方法简单，重复率高，通过室内实验验证了制作的微裂缝岩心可以用于钻井液封堵材料的封堵性能评价,为微裂缝封堵评价实验提供了岩心模块，弥补了使用缝板模拟裂缝表面光滑和采用砂床钢珠砂盘等孔隙介质换算裂缝开度的不足。

关键词:微裂缝;裂缝模拟;人造岩心;封堵评价;钻井液封堵

Abstract:

The cores with micro cracks were manufactured with metal foil and cementitious materials of different thickness, together with external cylinder of high temperature and high pressure water loss instrument and mud cup, the evaluation on micro crack plugging can be carried out. The verification is made by micro observation method and flow calculation method, the result shows that the micro cracks surface has a certain roughness and fracture opening is in accordance with the experimental design; the minimum crack opening is 3.33μm and the length of crack is 5～10cm. The manufacturing method of micro crack core is simple with high opening similarity. It is verified that the laboratory-made crack can be used to evaluate the plugging performance of drilling fluid plugging material, which provides core module for the evaluation experiment of micro crack sealing, and makes up the shortcomings of smooth crack surface by crack plate simulation and crack opening conversion when using porous media of sand bed, steel balls and sand plate.

Key words:micro crack; crack simulation; artificial core; plugging evaluation; drilling fluid plugging