新型离心机钻井液回收技术在3300m长江天然气管道穿越工程中的应用

3 300m长江天然气管道穿越工程穿越距离超长,地质条件复杂,主要穿越地层为粉砂层、细砂层,钻井液的回收处理是一个难题。为此,针对传统的钻井液回收系统及新型离心机钻井液回收系统开展了大量的对比试验。结果显示:在粉细砂层中,钻屑颗粒的粒径大多小于75μm,传统钻井液回收系统常用的筛网粒径最小为125μm,无法有效去除钻井液中的有害固相,若采用进一步增大筛网目数的方法,又会导致施工中钻井液回收的功效低;而采用新型离心机清除钻井液中的固相不增加钻井液体积,不必补加大量处理剂,有利于降低钻井液成本,同时对钻井液的性能影响小,有利于井下正常钻进。最后结合试验及应用情况,还就离心机钻井液回收技术的适用性问题提出建议:①在中、粗砂以上地层的穿越施工中,新型离心机较之于传统钻井液回收处理技术存在一定的劣势,此时不应盲目使用该技术;②中速离心机回收处理钻井液技术适用于在粉细砂地层中的穿越施工,而高速离心机回收处理钻井液技术更适用于在黏土类地层中的穿越施工。

A new centrifugal pump used drilling mud recycling system in the Jiangyin Yangtze River Crossing Project 3300 m HDD

Apart from the long distance and complex geological settings, the crossing strata are mostly powder sand bodies or fine sand bodies in the Jiangyin Yangtze River Crossing Project 3300 m HDD. This brings about great trouble in the recycling of drilling mud. In view of this, a number of comparative experiments were carried out between the traditional and new centrifugal pump used drilling mud recycling systems. Most of the particles in drilling cuttings were less than 75 μm in size so the harmful solids in the mud could not be separated by the tradition drilling recycling system with the screen mesh size of 125 μm at the minimum. If only by increasing the mesh numbers, the drilling mud recycling efficiency would be reduced. However, this new centrifugal pump used new drilling mud recycling system needs neither the increase of drilling fluid volume nor additional treating agents. As a result, the drilling fluid cost is thus cut down and the negative impact on the drilling mud performance is also limited, which will be helpful for the normal drilling in this project. Moreover, according to the experimental studies and actual application, we also put forward the following suggestions for the adaptability of this new centrifugal pump used drilling mud recycling system. First, unlike the traditional one, this recycling system will not be blindly applied to the crossing of such moderate and coarse sand bodies. Second, medium speed centrifuge pumps are adaptable for the powder and fine sands strata, while high speed centrifuge pumps better for clay strata.