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

Abstract

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. Introduction The Oil and Gas industry today requires better technologies to tap challenging reservoirs for sustained production of hydrocarbons in the future. Drilling of complex wells, such as extended reach, horizontal, multilateral, hostile environment (HPHT) and the like, has already been witnessed. Yet the focus remains on drilling similar Wells faster and cheaper without compromising the Well deliverability. This requires innovation and creativity in technology development while at the same time, and more importantly, willingness and commitment from Management to push for change and put new technologies to test. Only then can these be fully developed and adapted universally for the over-all benefit of the E&P Industry.

Formate Drilling and Completion Fluids: Evaluation of Potential Well-Productivity Impact, Valemon

“…Use of cesium formate as both drilling and completion fluid is particularly advantageous for wells completed with SASs because the plugging potential is reduced. The first use of cesium formate on a Statoil-operated field, and indeed worldwide, was on Huldra (Saasen et al 2002). Table 3 provides an overview of the Statoiloperated fields from the Norwegian Continental Shelf in which K/Cs formate has been used.…”

“…This gas/condensate field, with an initial reservoir pressure of 675 bar (9,790 psi) and temperature of 150 C (302 F), was in operation between November 2001 and September 2014. The wells were drilled and completed with 300-mm single-wirewrapped screens by use of 1.9-sg K/Cs formate brine (Saasen et al 2002). To avoid fluid losses to the formation and for filtercake repair, the screen-running fluid contained 30 to 40 kg/m 3 of calcium carbonate particles.…”

“…Formate brines have been used over a number of years as drilling-and-completion fluids for HP/HT fields (Howard 1995;Bungert et al 2000;Saasen 2002;Simpson et al 2005;Oswald et al 2006;Berg et al 2009;Qureshi et al 2008;Downs 2011;Olsvik et al 2013). Olsvik et al (2013) summarized the results from eight HP/HT fields in which cesium formate was used as the completion fluid in conjunction with a cesium-formate drilling fluid or oil-based mud.…”