Drilling efficiency depends on several dynamic factors and challenges. Horizontal drilling well design is critical to maximizing production and reservoir contact particularly cases in which several fluid engineering aspects affect drilling. Challenges increase when transitioning from horizontal to extended-reach drilling (ERD); however, minimizing metal-metal or metal-formation friction is vital. This paper presents a detailed study of laboratory testing of a range of lubricants and software simulation models of a true drilling environment to minimize friction.
For nearly a decade, efforts to reduce friction have focused on engineering the lubricant only without taking into consideration additional factors that could help diminish friction. The challenges of drilling reservoirs are numerous; however, the availability of intelligent software allows for replication of the actual conditions precisely enough to design and drill wells with minimum friction, while taking into account the numerous aspects affecting success. A detailed laboratory study that included software simulation was conducted to create a true ERD environment model with the goal of creating a plan to reduce friction; thus, improve production.
During one of the ERD intelligent projects, the service company team successfully simulated a scenario showing how the drilling fluid behaves under downhole conditions. Taken into consideration were temperature and pressure, the effect of tripping pressures on the equivalent static density (ESD), the effect of drilling parameters on equivalent circulating density (ECD), and the effect of lubricants on performance of different types of fluid design. A comprehensive study of all the parameters was completed, and their effect on drilling performance was determined. Both laboratory-prepared fluids and field fluids were further studied for high-pressure/high-temperature (HP/HT) rheology, lubricity, tripping pressure calculations, and ECD predictions to identify any gaps. Both data sets were consistent, allowing for excellent predictions for the fluid performance when well geometry is known.
A wide range of lubricants, both solid and liquid, and their effects were studied as well as the effect of using ester-based oil to formulate nonaqueous synthetic fluid. The study was extended to include both clay-based and clay-free invert emulsion fluids (IEF), including variable concentrations of ester-based fluid at different oil/water ratios and with different types of lubricants to present a comprehensive overview of all aspects of lubricity.