Application of Drilling Fluid Zero-discharge Technology in Bailu Lake Multi-well Pad

The Bailu Lake multi-well pad is located in a scenic area where environmental protection requirements are tough and solidifcation of waste drilling fluid for burial is prohibited. Multi-well pad technology was adopted in the drilling of 43 wells in this area to conform to the environmental protection requirements. Diffculties encountered during drilling included fast drilling, large amount of drilling fluid to be treated, reuse of fltered water, too much equipment which occupied large area, tough requirements on drilling fluid for drilling long open section, hydration and swelling of the shallow shales, and instability of the deep borehole wall. A calcium chloride drilling fluid was chosen to drill these wells. The coarse drill cuttings, without treatment by additives, were separated out from liquid phase and solidifed. The fne drill cuttings, on the other hand, were fltered under pressure to remove the liquid phase. Since the additives were added in solution form instead of being added directly into the drilling fluid, time required for the separation of the fne cuttings and liquid phase was shortened from 60 min to 20 min, and the maximum treatment rate reached 9 m³/h. Furthermore, the pipeline between the cuttings agitator and the flter was modifed, adding a vertical hydraulic piston charging pump to enhance treatment effciency. An auxiliary water flushing pipeline was installed on cutting trough to avoid the piling of cuttings therein. Drilling practice has shown that in multi-well pad drilling, using drilling fluid zero-discharge technology and environmentally friendly drilling fluid formulation can satisfy the needs of tough environmental protection and reuse of drilling fluid. The rate of penetration can also be greatly improved, effectively reducing drilling cost.