欠平衡钻井NW无固相充气钻井液的研究

为了有效配合欠平衡钻井开发低压低渗透气藏，最大限度地保护气层．研制了NW无固相充气钻井液。该钻井液的特点是可避免钻井液中的固相颗粒堵塞储层孔隙，抑制性强，减少滤液进入储层，即削弱水锁损害，保护储层岩石孔隙的连通性；小阳离子具有优先吸附形成一层阳离子保护膜的特点，其分子结构中的憎水基团．起到阻止水分子侵入的作用，进而削弱由低压低渗储层天然渗吸效应产生的水锁损害；司时钻井液滤失量小，仅约为10mL，而且钻井液具有强抑制性，可以减小钻井液对油层岩石渗透率的影响，达到保护储层、增加采收率的目的。该钻井液可满足充气工艺要求。此外，该钻井液密度连续可调，能有效降低液柱压力．形成泡沫群体结构，具有群体封堵、疏水屏蔽及特有的流变特性等良好特性，防止低压地层漏失，保护气层；配方简单，维护使用方便，能够很好地满足欠平衡钻井工程的需要。

Study on NW solids free aerated drilling fluid for under-balanced drilling

NW solids free aerated drilling fluid is developed to suit for the development of low pressure and low permeability gas reservoirs combining with the use of under-balanced drilling, and to maximize the efficient of reservoir protection. This drilling fluid is free of solids, thus avoids the risk of solid fines blocking the formation porosity; it has strong inhibition, and can minimize the invasion of drilling fluid filtrate into the formation, i. e. , reduce water blocking damage and protect the communication between the formation pores. The light weight cationic ions has the characteristic of priority adsorption, which forming layer of cationic protective film; the hydrophobic groups in its molecular structure can prevent the invasion of water molecules thus reduce the water blocking damage caused by natural seepage effect in the low-pressured and low permeable formation. Little filtration is detected for the drilling fluid, which is only about 10mL; and it has strong inhibition, which minimizes its influence on permeability, thus protects the formation and enhances oil recovery. This drilling fluid meets the requirements of aerated drilling technology. Furthermore, its density is continuously adjustable, it can effectively drop hydraulic column pressure, it can form group-foam structure, and has such features as group plugging, hydrophobic shielding and special rheology, and it can also prevent lost circulation and protect gas reservoir. This drilling fluid is easy for field use and maintenance, and can perfectly meet the requirements of under-balanced drilling.