How Water Depth Affects Extended Reach Drilling

Abstract

Abstract Over the last years, the drilling of extended reach wells (ERW) has become almost common practice in the oil industry. Although it still poses many technical challenges, successful applications such as the ones at Witch Farm, UK or in the South China Sea spurred the interest in ERW by the operators. In parallel, with the push for even further lateral displacement of wells, another technology frontier emerged for drillers: Extended reach wells in deepwater. The majority of the extended reach wells are drilled from onshore sites to reservoirs that are situated under sensible locations like preserved nature or urbanized areas. Extended reach wells drilled from fixed platform installations in shallow water usually are aimed to reach outer parts of reservoirs that otherwise could not be developed economically. In deepwater, ERW allows the use of dry completion platforms such as TLP or SPAR. It improves flow assurance and reduces the cost of the well and the future interventions. The paper at hand gives an overview on the effects of water depth on extended reach drilling (ERD) and has been divided in two sections. The first section is aimed to provide a general overview and examine the direct impact of water depth and pressure gradients on great displacement wells. It presents a number of ideas and practices currently used by operators. It also discusses applied solutions obtained from the associated literature and from interviews with experts in several service companies. Among others, new technology related to hole cleaning, torque and drag reduction and ECD management are discussed. The second section of this paper will look at possible solutions to the engineering challenges based on analytical methods. Tools such as rotary steerable technology, LWD, high torque drillpipe, non-rotating stabilizers and drillpipe protectors, hydraulic by pass subs and others are analyzed as part of an integrated planning approach. Several effects that different water depths scenarios have on ECD, torque, drag and formation pressure gradients are simulated, and discussed. Introduction It is common to think about ERW as directional wells that have the displacements much higher than the total vertical depth (TVD). It is also acceptable to use the ratio between horizontal displacement and TVD (DTVD) to classify directional wells. According to this relation, wells could be classified as follows