Study On Water-Based Drilling Fluid System For Deep Exploration Well Of Daqing

In the drilling process, because of the geothermal gradient and formation pressure gradient, the deeper the borehole is, the higher the temperature and pressure of the wellbore get, and so the mud will lose original performance easily under the high temperature. And, the high pressure tends to make the borehole wall unstable, which causes stuck and other complex accidents. Therefore, how to deal with the HTHP is the primary problem which will be met during the drilling of deep well and extra-deep well. In the recent years, the exploration and development of deep oil and gas in DaQing oil field is reinforced. The current drilling fluid can hardly meet the need of deep well drilling, so the water based drilling fluid system which is applicable to deep exploration well in Daqing is studied. Through trials and errors, the compatibility of this mud and the additives is tested and the optimal water based drilling fluid composition is got: 5%Bentonite +0.4%Na₂CO₃ +3%KFT +1.0%GWJ +1.5%TGT +1.0%YGY180 +1.0%SF260 +1.0%lubricant +0.1%KOH +1% BST-â…¡ +1%YGB-1. The compare between this water based drilling fluid system and some commonly used drilling fluids systems indicates that this drilling fluid system has evident advantages in cave in preventing, high temperature resisting, solid carry capacity and formation damage controlling. The water based drilling fluid system developed in laboratory is tested in Daqing oil field. The laboratory experiment and on-site trial show that the water based drilling fluid system is stable in rheological property and can carry cuttings and clean wellbore effectively. Its thermal stability is excellent and it can stabilize the borehole wall in a good condition. The water based drilling fluid also can control formation damage and do no harm to environment. The above proves that water based drilling fluid system is a qualified one to deep exploration well of Daqing oil field.