A Rational Approach to Multilateral Project Planning

Abstract

In the past, junction construction technology has driven the design of multilateral wells. This practice has led to technical successes that may or may not have met all of the operator's desired well objectives. These projects have often been regarded as less than successful from an economic point of view. This regard is partly due to the way that junction construction has been viewed. Junctions are presently classified by looking at the technical differences in how they are constructed, such as TAML levels (Technology Advancement - Multi Laterals)1. Although this method is suitable for looking at junction construction complexity, it does not address directly what the junction does in service. Another approach would be to drive the design using information about reservoir/production requirements. Looking at functional groups of junction features will allow the drilling or completions engineer to make sense of the myriad of available junction systems. This technique can help optimize the multilateral junction type selection for a given project. The process of planning multilateral projects from conception through well design will be discussed with a focus on using a functional classification map to clarify the junction requirements. The Functional Classification Method will assist engineers in comparing equipment options. This comparison is accomplished by, first, defining the reservoir and economic drivers, and, then, by selecting the appropriate junction attributes. Furthermore, the method will provide a process for assembling the data required to prepare the final well design and to prepare precise tender documents. To illustrate this method, recent examples from the Middle East will be presented. Introduction Historically, drilling engineers have struggled to design a well that would accommodate a given multi-lateral completion while meeting all of the reservoir depletion requirements. As a result, there have been a number of failures when attempting to install these systems. Looking at multi-lateral technology and its real function in the oil industry, it becomes apparent that it is not a drilling tool at all. Instead, it is a reservoir depletion tool. Shifting the ownership of this technology provides an opportunity to see the planning process in a new light. The concept of multi-lateral drilling is essentially one of reservoir depletion economics. It is one answer to the question of how to get the most production for the lowest cost. By starting the planning effort in the reservoir camp, the equipment selection process is enhanced. Only after the reservoir mechanics are considered and the depletion requirements defined, can an unbiased judgment be made regarding equipment selection. To aid in this selection, an optimized multilateral planning process was developed. The process map will guide the engineer to a number of junction attributes that can then be used to select and compare various vendor systems. In the event that no systems perfectly match the required attributes, the information can be used as the basis for a compromise. If no compromise is sufficient, this process will provide the basis for tendering a request to design/build the required system2. All desired outcomes from a drilled well fit in one of two categories: to obtain information or to promote hydrocarbon retrieval. No matter what the multilateral well design, or which equipment is used in the well, multilateral technology's only purpose is to do these things more effectively or more economically. The challenge is to provide only the functionality that is essential to meeting the minimum well requirements. Then functionality that is desired but not necessary can be evaluated on a cost-benefit basis prior to acceptance to the well plan.

Mature Field Re-entries Utilizing Level 4 Multilateral Technology

“…The key, then, is to promote those multilateral projects with the maximum added value and sticking with them through the learning phase to the point of reaping the greatest economic returns. 11 To date ConocoPhillips XIJIANG have already completed 18 multilaterals, including 1 each TAML Level 1, 1 each TAML Level 3, 15 each TAML Level 4 (10 of the 15 TAML Level 4 are constructed using only a single hollow whipstock system that this paper is based on. See Table 1.)…”

Rapid Planning and Execution of the First Multilateral Well in the Gulf of Thailand: Results and Lessons Learned

“…Had, by chance, the first two wells to penetrate these zones been spaced further apart, and thereby initially identifying a larger oil volume, the 65-1 sand might have been identified as a horizontal target earlier than what actually occurred. It was not until the KPWD-29 penetrated these zones on February 1, 2006 and defined the northern extent of the oil pay (see Figures 2,3 and 4) that it became clear that both zones were candidates for production via open-hole laterals, rather than just the 69-1 sand alone. Two weeks later the KPWD-13 delineated the southern extent of the oil pay.…”