Abstract

This paper pertains to the technological development of a completely integrated landing system that provides the ability to extend the deepwater drilling and completion envelope. This system is comprised of an elevator, slipless spider, and landing string all specifically designed to land heavy casing strings in deepwater wells thus overcoming the load limitations of conventional equipment. All stages of evolution are analyzed including research, development, design, verification testing, manufacturing, proof testing, running, handling, and actual case histories detailing field use. Actual verification testing loads were over 5,200,000 lbs and proof testing loads were 3,000,000 lbs. Unique manufacturing challenges and solutions associated with the production of ultra-thick wall landing strings with 2,000,000 lbs super premium yield ratings¹ (90% remaining body wall) are presented in detail.

Introduction

As the measured depths of deepwater wells increase towards and beyond 30,000 ft, the wells become significantly more difficult and costly to drill. Deepwater wells require larger casing programs with much heavier loads than previously experienced. A completely integrated landing system is required that delivers optimum load carrying capacity to handle the longest and heaviest casing loads and is constructed in a manner which enables for minimum time on location. Some operators have opted to run the otherwise very long casing strings as a liner and tieback, to eliminate the need to run a very heavy load. This adds cost through increased rig time and the additional expense of the liner and tieback hardware. This increases risk by running an additional operation at such a critical stage in the well that could otherwise be eliminated and heightens design concerns associated with compression loading on the casing tieback connections. Other operators have opted to “qualify” conventional equipment typically comprised of a mix of elevators, slips, and landing strings that were developed independent of one another through a test program integrating the various individual components. A technological development was needed having the capacity of supporting very large loads required in deepwater operations without 1) the limitations of conventional slip-based equipment, 2) the inefficiencies and HSE concerns of conventional non slip-based equipment, 3) the expense and risks associated with dividing long casing strings unnecessarily into liner and tieback arrangements, or 4) the investment of man-hours and expenses trying to “prove out” conventional equipment.

The LAST® System (Landing And Slipless® T echnology), provided^2,3,4,5,6 by Oil & Gas Rental Services, Inc., was developed and meets all of the criteria for BP America, Inc. in the current Thunder Horse deepwater drilling and completion program on Transocean's drillship "Discoverer Enterprise". The profiles of the 5-1/2" and 6-7/8" landing strings are shown in Figures 1 and 2, respectively. The performance properties are detailed in Table 1.

BP has been utilizing the “Discoverer Enterprise” to conduct drilling operations in the central Mississippi Canyon region of the Gulf of Mexico for 1-1/2 years. This rig is equipped with latest generation equipment including dual derrick operations with a 2,000,000 lbs load rating. The Thunder Horse project consists of several wells over 20,000 ft deep in water depths of over 6,100 ft, all of which are shown graphically in Figure 3 in relation to other extended reach wells in the industry.

Several experiences and lessons were documented during the extended field use of the LAST system. One well in particular was recently drilled and experienced one of the heaviest loads in the deepwater Gulf of Mexico. The maximum actual hook load encountered during operations was over 1,700,000 lbs. A wellbore schematic of this well is shown in Figure 4.

Summary of Conventional Equipment Limitations

Landing strings are specifically designed to carry the very high tensile loads generated by long, heavy casing strings. For simplicity, the handling equipment used to run these landing strings can be categorized into slip-based and non slip-based equipment.