水基聚乙二醇钻井液页岩稳定性研究

A STUDY OF SHALE STABILITY OF WATER-BASE POLYETHYLENE GLYCOL DRILLING FLUID

钻井过程中，由于钻井滤液的侵入，地层中的粘土矿物发生水化、膨胀、分散，削弱了岩石的力学强度，导致井壁失稳的发生。文中简述了聚乙二醇钻井液页岩抑制机理：浊点行为、协同作用、渗透作用。结合室内实验分析了影响聚乙二醇钻井液抑制作用的因素。当温度达到聚乙二醇的浊点温度后，聚乙二醇从溶液中析出，封堵页岩裂缝。当在聚乙二醇钻井液中加入合适的无机盐后，无机盐与聚乙二醇起协同作用，提高了聚乙二醇的页岩抑制性能，达到稳定页岩的目的。

Owing to the filtrate invasion of drilling fluid during drilling, the mechanical strength of rock is weakened because of the hydration, swelling and dispersion of clay minerals in strata, which causes the borehole wall to be unstabilized. The shale inhibition mechanisms of water-base polyethylene glycol drilling fluid, i. e. cloud point behaviour, synergetic effect and osmosis, are simply stated and in combination with the laboratorial data, the factors influencing the shale inhibition caused by the water-base polyethylene glycol drilling fluid are analyzed in the paper. When the temperature has reached to the cloud point temperature, the polyethylene glycol begins to be separated out from the solution to seal the fractures in the shales; and when a certain of inorganic salts have been added into the water-base polyethylene glycol drilling fluid, the shale inhibition caused by polyethylene glycol can be enhanced because of the synergetic effect of inorganic salts on polyethylene glycol, thus achieving the target of stabilizing shales.