Automatic Inclination Controller: A New Inclination Controlling Tool for Rotary Drilling

Abstract

Abstract The working principles, structural features and application of Automatic Inclination Controller(short in AIC) designed by Professor Su Yinao are introduced in this paper. It includes the analyses of controlling principles of the tool and the mechanical properties of the BHA with AIC. As a new type of adjustable stabilizer, AIC provides one down hole closed-loop system which relies solely on hydraulic feedback. The BHA with AIC reduces the number of round trip and saves drilling costs. It especially meets the requirements of China's oil fields. Introduction Benefits of Extended Reach and Horizontal Drilling With the development of drilling technology, many petroleum companies and operators have begun to put their more attention to horizontal drilling in order to reduce overall development cost and upgrade recovrey efficiency. The economic benefits of horizontal drilling have been clearly recognized. In China, a large part of reserves can be developed with horizontal well technology. By the end of 1997, there were totally 160 horizontal wells drilled in 14 oilfields on land.1 The drilling cost of horizontal well has been reduced by 1.5~2 times of vertical wells. ERD is the development of highly deviated directional well, which has the long high-angle holding section and long horizontal displacement. It can be applied to exploit offshore oil and gas field. In some cases, it is even feasible to develop offshore reservoirs from land, eliminating costly offshore platforms. The potential benefits of fewer platforms are illustrated by examples of Wytch Farm projects. The seventh well(1M-05SP) drilled at Wytch Farm, had a reach of 8035m, which set the world record for reach at the subject reservoir depth. In South China Sea, the 24–3-A14 well had total depth of 9238m with a reach of 8060.7m, which produced remarkable economic benefit. Development of Directional Drilling Technology Directional drilling technology can be divided into three major categories: conventional rotary drilling, motor-based steerable systems and recently rotary closed loop drilling systems. Rotary Drilling: The conventional rotary drilling technique involves kicking off the well in the desired direction with a bent sub and a Positive Displacement Motor(short in PDM). On completion of the kick-off, the PDM and bent sub assembly is pulled out of the hole and replaced with a rotary building assembly. On drilling to desired inclination, the building assembly is pulled of and replaced with a holding assembly. If the inclination and azimuth begin to wander from the planned well path, it is needed to pull out of hole to pick up a PDM and bent sub to correct the dierection of the hole.2 The disadvantage of the method is the requirment of pull out of the hole in order to change the BHA if any adjustment to the direction or inclination is necessary. This may lead to the increase of auxiliary operating time and raise the drilling cost. Steering Drilling: Fig. 1 gives the structural diagram of BHA of the PDM based steerable system. In the light of present situation of on land in China, the system consists of an adjustable bent motor, single-shot survey and cone bit(short in BS-DHM). It adjusts between orientation in the desired direction and being in a rotary mode alternatively, which don't need to trip and modify the BHA. Benefits of Extended Reach and Horizontal Drilling With the development of drilling technology, many petroleum companies and operators have begun to put their more attention to horizontal drilling in order to reduce overall development cost and upgrade recovrey efficiency. The economic benefits of horizontal drilling have been clearly recognized. In China, a large part of reserves can be developed with horizontal well technology. By the end of 1997, there were totally 160 horizontal wells drilled in 14 oilfields on land.1 The drilling cost of horizontal well has been reduced by 1.5~2 times of vertical wells. ERD is the development of highly deviated directional well, which has the long high-angle holding section and long horizontal displacement. It can be applied to exploit offshore oil and gas field. In some cases, it is even feasible to develop offshore reservoirs from land, eliminating costly offshore platforms. The potential benefits of fewer platforms are illustrated by examples of Wytch Farm projects. The seventh well(1M-05SP) drilled at Wytch Farm, had a reach of 8035m, which set the world record for reach at the subject reservoir depth. In South China Sea, the 24–3-A14 well had total depth of 9238m with a reach of 8060.7m, which produced remarkable economic benefit. Development of Directional Drilling Technology Directional drilling technology can be divided into three major categories: conventional rotary drilling, motor-based steerable systems and recently rotary closed loop drilling systems. Rotary Drilling: The conventional rotary drilling technique involves kicking off the well in the desired direction with a bent sub and a Positive Displacement Motor(short in PDM). On completion of the kick-off, the PDM and bent sub assembly is pulled out of the hole and replaced with a rotary building assembly. On drilling to desired inclination, the building assembly is pulled of and replaced with a holding assembly. If the inclination and azimuth begin to wander from the planned well path, it is needed to pull out of hole to pick up a PDM and bent sub to correct the dierection of the hole.2 The disadvantage of the method is the requirment of pull out of the hole in order to change the BHA if any adjustment to the direction or inclination is necessary. This may lead to the increase of auxiliary operating time and raise the drilling cost. Steering Drilling: Fig. 1 gives the structural diagram of BHA of the PDM based steerable system. In the light of present situation of on land in China, the system consists of an adjustable bent motor, single-shot survey and cone bit(short in BS-DHM). It adjusts between orientation in the desired direction and being in a rotary mode alternatively, which don't need to trip and modify the BHA.