New Shock Resistant Cement Reduces the Required Time for Side-Tracking from KickOff Cement Plugs

Abstract

The process of sidetracking an existing borehole with a balanced cement plug has historically been time consuming and problematic for the drilling industry.In many instances long drilling times or even multiple plugs are required to achieve the objective of sidetracking the well. These problems lead to increased drilling time and increased cost for the operator. Traditional cement slurry systems for sidetrack applications have been focused on the development of high compressive strength through reduced water content. Conventional high compressive strength cement systems exhibit low resistance to impact and low resistance to fracture propagation through the set cement. Recent developments in oil well cement system have incorporated a unique micro-ribbon technology with an optimized particle size distribution to increase the durability, load bearing capacity and resistance to fracture propagation of set cement. Field tests with these cement systems have shown substantial improvements over conventional cement slurries in terms of plug success rate and time required to achieve the objective of sidetracking the well. These improvements have resulted in significant reductions in the total cost of the operation of sidetracking wells. This paper will discuss the improved mechanical properties of these new cement systems and the success of the numerous field tests. Introduction Borehole sidetracking operations with cement plugs is a well-established and long-standing technique. This technique consists of placing a plug of cement in the borehole, allowing the cement to establish compressive strength, then using the cement plug to deflect the bit away from the current borehole starting anew open hole section. Difficulties in this operation are also well documented and long-standing [1–6]. As drilling cost increased and the level of directional drilling increased the cost associated with the failures of sidetrack cement plugs gained more attention. These problems continue to receive attention today. Many studies have been conducted to improve success rates of open hole kickoff plug placement [1–4]. Most of these studies have focused on improving portions of the workflow process associated with plug placement and slurry design methods. Others have focused on developing recommended practices for the sidetracking operation as a whole [2]. New tools have been proposed and developed to improve the placement efficiency of cement slurries [5–6] or provide mechanical alternatives to cement plugs in the open hole [6]. Much less effort has been directed toward optimizing the cement systems utilized to achieve the sidetrack. Traditionally, cement system design for sidetracking operations has focused on maximizing set cement compressive strength while optimizing other traditional properties such as pumping -time, rheology, slurry stability, fluid loss, etc. Some work has been focused on the development of cement systems that reduce the rate of penetration when drilled[7]. This work has been focused on the addition of particles with a high degree of hardness to the slurry. Reducing the rate of penetration of the slurry when drilled would seem to represent an important characteristic of aset cement system used for sidetracking operations. When properly applied, these lessons learned and the cumulative set of placement and design methodologies developed from past efforts have provided substantial rewards to the industry. However in some areas, for example regions with extremely hard formations, problems still exist even if proper placement and proper conventional slurry design are followed. This paper will outline a new cement slurry that focuses on optimizing the mechanical durability of the set cement through the implementation of optimized particle size distribution slurries with metallic micro-ribbon technology and the successful field testing of these slurries in over 25 wells. Successful implementation of this new system in sidetracking operations for a major operator in Abu Dhabi has resulted in significant improvements in the efficiency of sidetracking operations and significant cost reductions resulting from rig time saved.

New Technique to Sidetrack Across Hard Formation in North Oman

“…To reduce such impact, recommended practices (Babasheikh et al 2003) have been developed to address certain operational factors, such as planning and laboratory evaluation of prejob conditions, cementing fluids, and placement.…”