A Systematic Approach to Drilling and Delivering Wells in Severely Depleted Sands at Ram Powell (GOM)

Abstract

Abstract Re-development drilling at Shell's Ram Powell prospect in the Gulf of Mexico targets profitable delivery of remaining hydrocarbons present in lower-volume reservoir pockets. Marginal economics put a strong focus on efficient operations, which are complicated by the technical challenges posed by severely depleted reservoirs (up to 6,000 psi differential pressure) that can only be accessed by drilling extended reach (ERD) wells. Specific challenges that had to be overcome in drilling recent Ram Powell wells include negotiating very narrow drilling margins, preventing major non-productive time associated with well control, lost circulation and stuck pipe events, and drilling the wells at optimum efficiency and favorable economics. This paper discusses the integrated operational plan that the Ram Powell team employed to successfully drill four recent ERD development wells and two slim hole sidetracks through substantial depletion while becoming one of the best-performing offshore operational teams in Shell. Specific tactics discussed include:a fit-for-purpose hole cleaning program for ERD and depleted wells;a mud weight and ECD strategy that exploits the naturally existing stress cage;an effective method to raise fracture propagation pressures in case of losses in induced or natural fractures;the use of flat-rheology synthetic-based mud to minimize barite sag and reduce ECDs;addressing the underestimated effects of temperature, annular pressure fluctuations and exposure time on wellbore stability and lost circulation;contingencies to deal with well control issues during a catastrophic loss;dealing with detrimental vibrations during depleted sand drilling Introduction Further development of the mature Ram Powell prospect (Fig. 1) faces the same challenge as seen in many brown-field developments around the world: how to extract remaining hydrocarbons in place in low(er) volume reservoirs in a cost efficient way? The dilemma here is that whereas it is difficult - if not impossible - to justify high cost wells from an economical standpoint, rather complex wells are required to access the oftentimes poorly accessible reservoirs scattered about the prospect. Main elements of complexity are the extended reach character and associated directional complexity associated with these wells, as well as the fact that they are no longer drilled under pristine reservoir conditions. Usually, historical production has led to significant reservoir depletion, leading to significant changes in pore-pressure and associated geo-mechanical changes. The challenges we were faced with at Ram Powell were in many respects unique. Ram Powell was one of the very first deepwater developments in the Gulf of Mexico1,2. As a result, at Ram Powell we are further into the field's production lifecycle than in many other Gulf of Mexico prospects, experiencing drilling problems that have rarely been seen before or experienced in similar severity. Moreover, a unique challenge was presented to the team by making the number of wells to be drilled in the re-development campaign dependent on the well delivery execution efficiency achieved. Achieving operational excellence thereby translated directly in access to more drilling and production opportunities. In the following, we will highlight how the Ram Powell team met the above-mentioned challenges, achieving a high degree of operational proficiency that made it one of the best performing teams in Shell E&P Co. We will discuss the nature of depleted sands and the challenges associated with drilling them, and present the elements of the systems approach that was adopted to drill highly successful wells. Depleted Drilling Challenges at Ram Powell Brown Field development from fixed structures presents complex drilling and completion challenges. The first stage of production of the primary targets, usually better-developed and higher-volume reservoirs, has usually produced a significant level of depletion. Further reserve recovery now requires penetration of these depleted zones with drainage points at much greater step-out than the original wells. This is the situation we face at Ram Powell.