超低渗透钻井液防漏堵漏技术研究与应用

在水基钻井液中加入一定量的零滤失井眼稳定剂可以形成超低渗透钻井液.介绍了超低渗透钻井液提高地层承压能力及防漏堵漏的机理.超低渗透钻井液对不同孔隙的砂岩、岩心和裂缝性地层具有很好的封堵能力,可以实现近零滤失;零滤失井眼稳定剂通过在井壁表面形成超低渗透膜及增强内泥饼封堵强度大幅度提高岩心承压能力.在大港油田和辽河油田多口井的现场应用中,超低渗透钻井液在长裸眼多压力层系或压力衰竭地层防止了漏失、卡钻和坍塌的发生,表明超低渗透钻井液能自适应封堵岩石表面较大范围的孔喉,在井壁岩石表面形成致密超低渗透封堵薄层,可有效封堵不同孔喉地层和微裂缝泥页岩地层.超低渗透钻井液封堵隔层承压能力强,能提高漏失压力和破裂压力梯度,相当于扩大了安全密度窗口.

Study and application of ultra-low permeable drilling fluid: lost circulation prevention and control

An ultra-low permeable drilling fluid comes into form when some zero-filtration hole stabilizing agent is added into a water-based drilling fluid. This paper describes mechanism of formation pressure bearing ability increasing and lost circulation prevention and control of this fluid. The fluid behaves excellent sealing/plugging property in sandstone of different permeability and fractured formation, which help realize approximately zero-filtration. In addition, by forming ultra-low permeable membrane on the surface of well bore and enhancing inner mud cake strength, the zero-filtration hole stabilizing agent increases the formation pressure-bearing ability substantially. In-situ using in several wells located in Dagang oilfield and Liaohe oilfield showed that, accidents such as lost circulation, pipe sticking and hole collapse were stopped in long borehole in multi-pressured formation and depleted formation. It indicated that ultra-low permeable drilling fluid could seal pore throat in a large range and a compact ultra-low barrier was formed on the stone surface. Leak pressure and break down pressure gradient were increased, and safe density window was enlarged.