在大北地区施工的井中,由于地面条件的限制,在施工的过程中,所使用的水总矿化度为:110000mg/L,Ca2+:1000mg/L,Mg2+:4500mg/L。由于所使用的水矿化度较高,地层造浆困难,在进入沙河街组前,降失水困难,导致井壁极不稳定。在该地区使用海水钻井液体系,较好的解决了在该地区施工的问题,同时也为在同样的条件下施工取得了一些经验。 In the wells constructed in the Dabei area, the total salinity of water used during construction was 110000 mg / L, Ca2 +: 1000 mg / L and Mg2 +: 4500 mg / L, due to the limitation of ground conditions. Due to the high salinity of water used and difficulties in formation of the formation, it is difficult to reduce water loss before entering the Shahejie Formation, resulting in a very unstable shaft lining. The use of seawater drilling fluid system in this area has solved the problem of construction in this area and gained some experience for the construction under the same conditions.