Bill W. Loughridge

Impact of Synthetic-Based Drilling Fluids on Oilwell Cementing Operations

This paper presents chemistries of new synthetic-based muds and describes how they affect cement-spacer design. The paper also shows how new fluids and spacers affect the hydraulic bonding of oilwell cements to casings and formations. It discusses the polarity and dispersibility of various synthetic-based fluids and how their chemistry influences cement bonding. Insights into designing new surfactant packages for displacement fluids are provided. Other oil-based fluids are reviewed and compared to the new synthetic fluids. Also presented are new fluid system formulations and other factors affecting drilling performance vs. cementing. Rising drilling and completion costs, along with an increased awareness of sensitive environmental concerns, have placed more emphasis on effective annular sealing during the primary cement job. Synthetic-based drilling fluids have strong oil-wetting characteristics. Therefore, the following considerations should be made before cement can be successfully pumped behind these fluids: (1) the annular fluid (drilling mud) should be physically displaced by another fluid, and (2) the displacement fluid should leave the casing and formation water-wet. Laboratory experiments testing compatibility and shear bond presented in this paper demonstrate techniques used for cementing behind the new synthetic-based drilling fluids.