Low-Impairment Mud System for Drilling Horizontal Wells Through Clastic Reservoirs in a South Oman Oil Field

Abstract This paper discusses the development, field experience, cost aspects and the consequences of using a low-impairment drilling fluid system for drilling horizontal wells targeted on clastic reservoirs in a South Oman oil field in the concession area of Petroleum Development Oman [PDO], The first horizontal well was drilled in January 1990 and by October 1992 a total of twenty three wells had been drilled and completed in the field. The first five wells were drilled using conventional water based systems. But once the horizontal well scenario had been proven, subsequent wells were drilled with a fit-for-purpose low-impairment drilling fluid system formulated for specific hole sections. Progressive changes in well and mud design, as well as the optimization of drilling practices, have resulted in significant reductions in drilling times and well costs and increased well productiviities.