Pushing the Limits: Improving Drilling Performance of High Temperature Gas Wells in Thar Desert in Sindh, Pakistan

摘要

Improving drilling performance leading to reduction in Well drilling time and the associated costs, without compromising the deliverability of the Well, is the primary objective of drilling engineering. Some of the major challenges faced by Drilling Engineers include damage to the pay zone while drilling the reservoir section, lost circulation problems, drilling of hard and abrasive formations and more. With recent advances in drilling-related technologies, these issues have been addressed and tremendous time and cost benefits have been realized. OMV has been drilling high temperature vertical gas wells up to 4000m in Sindh, Pakistan. For drilling the reservoir section, OMV Pakistan pioneered the use of high temperature Formate Brine systems. These are solids free, high temperature stable drilling fluid systems which incur minimal damage to the reservoir. Application of these has yielded excellent results in terms of drilling as well as reducing skin damage. To combat lost circulation, OMV Pakistan introduced and successfully implemented the concept of Advanced Engineering Fibers (AEF) mixed in mud to control the losses in fractured limestone formation. The AEF-mud pill soaks, or can be squeezed, into the formation and immediately creates a fiber-net barrier preventing further losses. The successful implementation of this technology is a landmark achievement in controlling mud losses. Through optimized bit design and selection process, OMV Pakistan was able to realize its goal of 'One Bit per Section' drilling. Well Sawan-11 was drilled to a depth of 3415m with a milestone single bit run of 1758m at an average ROP of more than 25 m/hr. The bit was pulled 'Green' with minimal damage to cutters. This resulted in less drilling time and tremendous cost saving. This paper presents accomplishments, experience, and lessons learned related to drilling in the Sindh area where the reduction of drilling time from nearly 3 months to around 3 weeks is an outstanding outcome of the "Pushing The Limits" concept.