Development and Application of a High Temperature High Filtration Rate Acid Soluble Lost Circulation Agent for Oil Based Drilling Fluids

High filtration rate lost circulation materials have several shortcomings such as inability to use at elevated temperatures, inability to mix with oil-based drilling fluids and low acid solubility etc. A high filtration rate lost circulation agent for use in oil-based drilling fluids have been developed to deal with these problems. This new lost circulation agent can be used at 150℃-190℃, and has acid solubility of 75.7%. It is composed mainly of a high softening point epoxy resin, a latent curing agent, and a highly acid soluble fiber, which has certain strength after filtering and piling. Laboratory evaluation experiment shows that this lost circulation agent can effectively consolidate after filtering, the plugging layer formed by the lost circulation agent after filtering has compressive strength that is greater than 4 MPa. The plugging layers formed in 1-5 mm fractures have compressive strengths that are greater than 11.5 MPa. The plugging layers do not cure at low temperatures and the curing time at elevated temperatures is 3.3-6.5 h, meaning that the use of this lost circulation agent is safe. A technology of using this lost circulation agent to formulate a high temperature high filtration rate acid soluble lost circulation slurry for use with oil-based drilling fluids has been used to control the loss of oil-based drilling fluid occurred on the well Yong-X. The operation temperature was 151℃, and the severe mud losses into the pay zones were successfully brought under control.