Wellbore Construction in the Deepwater and Ultradeepwater Gulf of Mexico - Build-To-Suit Technologies
Authors: Denney Dennis 
Published: February 2015

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 136840, ’Build-To-Suit Technologies for Wellbore Construction in the Deepwater and Ultradeepwater Gulf of Mexico,’ by Tarab H. Ali, SPE, Rohit Mathur, SPE, and Nitin Sharma, SPE, Baker Hughes, prepared for the 2010 SPE Deepwater Drilling and Completions Conference held in Galveston, Texas, 5-6 October. The paper has not been peer reviewed.

Deeper reservoirs in more-challenging environments are being explored.  In the Gulf of Mexico (GOM), major operators are shifting focus toward deepwater and ultradeepwater oper-ations. Technologies (customized to meet operators’ specific challenges) that have helped operators reach their goals are reviewed. Also, technologies are examined that are still at the inception stage, but hold potential for development and use in ultradeepwater operations.

Introduction

Some major challenges encountered in the deepwater and ultradeepwater GOM include water depths to 10,000 ft; down-hole pressures exceeding 20,000 psi; salt, tar, and rubble zones; complex stacks of turbidite/sandstone reservoirs; tight-sandstone reservoirs (i.e., permeability less than 10 md); real-time data transmission from downhole tools; and deep reservoirs. Each of these challenges, individually and in combination, must be met with precise planning and selection of technologies to achieve the desired results. It has been a challenge for operators and for service providers to package tools and services that can control these challenges during wellbore construction. Various case studies discuss specific technical solutions to meet these challenges.

Case 1: Real-Time Drilling Dynamics

Drilling optimization is required in the bottomhole assembly (BHA), which leads to extensive planning in a well design. Modeling programs are used to select best-fit parameters for each bottomhole section on the basis of tool technical limits, expected formations, rig limitations, and wellbore geometry. Drilling dynamics affects the drilling of a well. Primarily, it is the result of the interaction between the bit and the changing lithology, the interaction between the drillstring and the hole at points of contact, and of drilling practices that control assembly stability. The key to preventing destructive drilling dysfunctions is a better understanding of the drillstring response to ever-changing mechanical conditions and acting proactively to mitigate dynamic vibration conditions.

Technologies exist for deepwater use to capture basic vibration-related information, such as lateral vibration, axial vibration, and stick/slip. Basically, these technologies are good for drilling-efficiency calculations and can be used to make changes in drilling parameters. Often, however, the destructive phenomena tend to couple together, producing a resonant frequency that has potential of additional harmful effects on the BHA. Therefore, use of an enhanced service to detect multiple drilling-dynamics phenomena and focus on optimization are needed for safe drilling of ultradeepwater wells. In addition to the damaging vibrations, such tools also capture the weight and torque acting on the assembly downhole.