Drilling Fluid Technology for Igneous Rocks in Ultra-Deep Wells in the Shunbei Area, Tarim Basin

Igneous formations in the Shunbei Block of Tarim Basin are characterized by severe instability of bore hole walls, higher risks of severe lost circulation, the coexistence of lost circulation and collapsing in long open-hole intervals, high friction resistances, bit sticking and other technical challenges. Under such circumstances, research has been performed to optimize formulas for drilling fluid systems. With consideration to the results related to coating inhibitors on the performance of drilling fluid, the performance of different filtrate loss agents, shielding effect of compound plugging agents, the ratio of compound lubricant and friction reducing capacities, a potassium amine-based polysulfide drilling fluid system was developed. Lab test results showed that the rolling recovery rate and linear expansion rate of igneous rock samples in the drilling fluid are 96.07% and 1.87%, respectively. The drilling fluid can effectively resist contaminaiton induced by 5% NaCl and 2% CaSO4. The newly developed drilling fluid system has been tested for drilling igneous formations in Well Shunbei1-3. The average enlargement rate of well diameter in Permian igneous rock is only 12.88%, and the drilling time in complex well section was reduced by 37.9 days in comparison with Well Shunbei 1-1H. No loss of circulation occurred in the Permian igneous well interval. The average enlargement rate of the well diameter in the diabase formation decreased by 15.7% compared with that of the Well Shunbei 1.The application of potassium-amine polysulfonated drilling fluid with a high inhibition and sealing performance solved the problems in ultra-deep well and igneous rock formation drilling effectively, it can be deployed extensively in the Block.