Mud Loss Control while Drilling with Oil Base Drilling Fluid

Oil base drilling fluids are generally the first choice in shale drilling because of their advantages such as low friction and weak shale swelling. Coexisting with the advantages of the oil base drilling fluids are their disadvantages, such as high drilling cost, especially when mud losses are happening, which always cause serious economic loss. To control losses of oil base drilling fluids into formations, a type A lost circulation material (LCM) has been developed, and its particle sizes analyzed. Experiments have been conducted to optimize the particle sizes for the effective and efficient control of oil base mud losses at different loss rates. The experimental results showed that the type A LCM has good compatibility with the drilling fluid used, good dispersity and high oil absorption rate. The type A LCM is resistant to high temperatures to 150℃, and penetrates into a sand bed for 1.0 cm with almost zero filtration. This LCM performs better than the same types of other LCMs in controlling seepage loss and mud losses into fractures. In flow experiments, the forward displacing pressure was 13 MPa, and the reverse breakthrough pressure was 1.2 MPa, indicating that the loss zones deposited with the type A LCM had high pressure bearing capacity and the deposited LCM was easy to remove. Composite LCM formulated with the type A LCM and other LCMs can resolve mud losses into fractures of 1-3 mm in size effectively. The mud loss control technology has been successfully used on the well Jiaoye195-1HF, reducing the drilling cost and the time required for drilling.