Universal Process for Benchmarking Drilling Fluid Performance
- Mario Zamora (M-I SWACO) | Judy McGlaughlin (M-I SWACO)
- Document ID
- Society of Petroleum Engineers
- SPE Drilling & Completion
- Publication Date
- June 2008
- Document Type
- Journal Paper
- 123 - 131
- 2008. Society of Petroleum Engineers
- 1.11 Drilling Fluids and Materials, 1.10.1 Drill string components and drilling tools (tubulars, jars, subs, stabilisers, reamers, etc), 1.1 Well Planning, 4.3.4 Scale, 4.1.2 Separation and Treating, 1.11.2 Drilling Fluid Selection and Formulation (Chemistry, Properties), 7.3.3 Project Management, 4.6.3 Gas to liquids, 4.1.5 Processing Equipment, 1.6 Drilling Operations, 1.12.6 Drilling Data Management and Standards
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A process has been developed to evaluate drilling fluid cost performance for a wide range of planning, intervention, and quality improvement activities. Meant to be universally applicable, the innovative process permits comparisons between similar and dissimilar wells drilled in the same or different global regions. It also can be used to contrast drilling fluid cost performance with operator-driven quality indicators to classify wells for front-end loading requirements for planning and to monitor actual-versus-planned performance during drilling.
Methods normally used for drilling performance are not well-suited for benchmarking drilling-fluid performance. The approach introduced in this paper is based on a simple ratio that compares mud cost of a well to a corresponding technical limit. The technical-limit relationship, which uses a profile index to characterize well complexity, was derived empirically from a large internal database representing a wide assortment of well types, drilling conditions, and locations.
This paper describes the development and implementation of this process. Several case studies are presented to demonstrate specific applications. Although the process was developed strictly for internal use, full implementation details are provided to encourage its use by others in the industry involved with service-quality initiatives.
Drilling is an engineering process fraught with complexity and variability that make global benchmarking efforts difficult. As such, performance comparisons mostly have been done on a well-by-well, actual-versus-plan basis. Recent industry service-quality programs implemented to address trends involving multiple drilling projects have met with varied success. Most seek to correlate drilling costs to key performance indicators (KPIs), individual drilling metrics, and parameters that integrate several KPIs and metrics into a single index. The Dodson Mechanical Risk Index (MRI), for example, is a de facto standard that considers well depths, mud weight, number of casing strings, and various key drilling factors (KDFs) weighted by their projected impact on drilling difficulty (Dodson 2000; Williams et al. 2001).
Successful benchmarking of drilling fluid costs has been more elusive. Consider the data scatter shown in Fig. 1, where mud costs are plotted versus total depth for 12,257 wells drilled between 1998 and 2005. This became a concern when mud-cost benchmarking was assigned a high priority for an internal service-quality management initiative. One of the objectives was to develop a universal process to facilitate comparisons between similar and dissimilar wells drilled in the same or different global regions under radically different drilling conditions. For example, the process should be able to compare drilling fluid cost performance on a 10,000-ft land well to one drilled in 10,000 ft of water.
The data in Fig. 1 were obtained from an internal database of conventional, deepwater, HTHP, and highly directional wells drilled under a broad range of downhole conditions by numerous operators in 57 countries. Drilling fluid costs ranged from less than $5,000 to over $15 million for an average of $232,500 (net present value of money was not considered). Maximum and average depths were 31,753 ft and 9,628 ft, respectively. The majority of extreme mud costs occurred in the Gulf of Mexico where massive lost circulation had to be tolerated in some sub-salt wells. Very high mud costs also were experienced in West Africa, the North Sea, and CIS.
Attempts to correlate mud costs to the more inclusive MRI were unsuccessful, primarily because of the indices on which KDFs focused: drilling rather than fluids, offshore rather than global, and critical rather than generic wells. Correlations improved when KDFs were replaced with common drilling fluid risks such as lost circulation, stuck pipe, wellbore instability, torque/drag, hole cleaning, barite sag, and others. The economic impact of these risks, however, varied greatly between different regions and well types. Moreover, the required data were difficult to extract and quantify.
Development of a new complexity index that retained some aspects of the MRI led to a different approach for benchmarking mud costs. The analytical method was integrated into a Quality Element Deployment (QED) process to address a wide range of drilling fluid planning, intervention, and quality improvement issues. Additionally, it made it possible to contrast drilling fluid cost performance with operator-driven quality indicators, to monitor actual-versus-planned performance during drilling operations, and to classify wells for front-end loading (planning) requirements.
This paper focuses on the development and implementation of the QED process. Case studies involving different drilling environments are presented to illustrate useful applications. Although the process originally was developed strictly for internal use, full implementation details are provided in order to encourage its use by others involved with service-quality initiatives.
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CFL/NFL Passer Rating. Wikipedia, http://en.wikipedia.org/wiki/Passer_rating.Downloaded 9 November 2007.
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