Traditionally, Non-Aqueous Fluids (NAF) have been used by a major operator to drill challenging wells in the Campos
Basin, Brazil. Significant advances in water based drilling fluid design in the recent years have allowed water-based drilling fluid performance to approach that of NAF. Exploration in the new frontiers and optimized development well projects in deepwater Brazil have required a different approach regarding drilling fluid design due long step outs, difficult well trajectory, and the possibility of drilling horizontal wells in one step, thus avoiding intermediate casing strings. Although NAF are an ideal candidate for those applications, environmental concerns and logistic demands are still an issue and alternatives should be considered.
HPWBM has been applied to replace NAF in some applications in deepwater and ultra deepwater (UDW) in the Campos Basin. This novel technology has been successfully applied to drill in UDW scenarios, reactive clays, dispersive shale, naturally micro fractured formation and horizontal wells. HPWBM characteristics are developed with:A new generation of encapsulation polymers;The use of amine chemistry to provide clay stability;The application of novel sealing polymer for shale stability; andExcellent mud lubricity characteristics.
The lessons learned, as supported by case histories and lab data have contributed to system modifications which have improved performance. This work has also identified attributes needed to complete a drilling fluid design for the difficult wells to be drilled in the new exploration and development areas. The evolution of HPWBM drilling fluid design will be discussed along with how decisions were made.
Introduction
Today the industry is drilling more technically challenging wells difficult wells. Exploration and development operations have expanded globally as the economics of exploration and production for oil and gas have improved with advancements in drilling technology. Advanced drilling operations such as deep shelf, extended reach, horizontal and deepwater are technically challenging, inherently risky and expensive. With consideration to reducing drilling problems such as torque and drag, stuck pipe, low rate of penetration and well bore stability; these wells are generally drilled with emulsion-based muds.
Nearly three quarters of the earth is ocean and a high prospect of hydrocarbon resources in addition to the other marine resources. That's why the industry is shifting from onshore drilling to offshore drilling. Published information indicates the presence of more than 20% of world's proven reserve in offshore geological structures. According to future production forecast of production reserves about 40–50% of future hydrocarbon recovery will be from offshore reserves. This is reflected by the increasing activity in the offshore environment with a gradual shift from shallow water drilling to deepwater drilling operations.
This scenario is particularly critical in the drilling exploration of offshore Brazil where the country faces the challenge of increasing oil production and reaching energy self-sufficiency within the next few years. Petrobras is well known for extended deepwater experience, however exploration in the new frontiers of ultra deep water face new challenges.
