Techniques and Materials for North Sea Plug and Abandonment Operations

Abstract

Plug and Abandonment (P&A) can easily contribute with 25% of the total costs of drilling exploration wells offshore Norway. The costs of running a P&A operation on some offshore production wells may have a cost impact similar to the cost of the original drilling operation. Therefore, cost efficient P&A technology is necessary to reduce cost. In this paper, qualified technology and materials for P&A is reviewed to act as a basis for P&A planning.This paper describes in detail requirements for P&A operations offshore Norway as well as normal practices for P&A. Well construction issues related to minimising the need for later P&A operations like proper primary cementing planning is discussed. P&A techniques and materials for P&A operations are reviewed to act as background information for future P&A planning on the Norwegian continental shelf. These techniques include operations ranging from milling to washing and squeezing cement or other materials. The materials being reviewed include swollen shale, concentrated sand, metal plugs like bismuth, as well as improved conventional cement systems. This work presents an overview of the well plugging and abandonment challenges, innovative potential barriers and case histories on the Norwegian continental shelf.

Mechanical performance of bentonite plugs in abandonment operations of petroleum wells

“…Although the technical effectiveness of bentonite plugs is recognized [18,19], there are still gaps regarding their application in oil wells as a barrier element in abandonment operations, especially in terms of mechanical integrity. In this context, it is necessary to consider the influence of the operational procedures adopted on the pellets placement inside the well [20], which can expose the material to different conditions in onshore and offshore environment [21], influencing the chemical interactions that occurs during hydration and/or the physical conformation of the plug. Furthermore, subsurface conditions may also impact mechanical properties, and are mainly related to the contact of the plug with the formation waters that saturate the reservoir significantly in mature wells, and generally presents a high electrolyte content [22][23][24].…”

Vehicle routing with endogenous learning: Application to offshore plug and abandonment campaign planning

“…When several wells are P&A'd together, making use of one or several available specialized vessels, we call this a P&A campaign. Even though P&A operations have been conducted for a long time (Calvert & Smith, 1994), the focus on P&A has increased during recent years due to the large number of offshore wells that are approaching the end of their life-time in established areas such as the North Sea and the Gulf of Mexico (Khalifeh et al, 2013;Kaiser, 2017). As P&A operations can be very time-consuming and costly, it is of interest to optimize the P&A process as much as possible.…”

Materials for Well Integrity: Performance of Setting Materials for Well Cementing Operation

“…A spongy structure was identified within the one-week-old sample, which is due to the formation of three-dimensional structures after polycondensation in geopolymerization reaction. The geopolymerization reaction leaves unreacted ingredients in the structure to various extents, while they react at a slower rate with alkaline pore solution until becoming part of the geopolymer matrix (Khalifeh et al, 2013). In this mix design, the unreacted rock-based source of aluminosilicate and GGBFS are indicated by blue and yellow arrows, respectively.…”