Is this the beginning of the end of weighted mud systems? An advanced well control practice called Managed Pressure Drilling (MPD) is staged to challenge the conventional drilling practice of when in doubt "weight it up". Formation overpressures have traditionally forced operators to weight-up mud systems in order to advance drilling operations while preventing formation fluids invasion. A direct consequence of increased mud weight is a dramatic reduction in drilling Rate of Penetration (ROP), requirement for additional casing seats/strings and increased well control risks due to kicks from losses. This drilling hazard has represented a major source of invisible or intangible lost time and hence, cost. A drilling hazard mitigation multi-well trial was carried out to investigate and quantify the reduction in ROP as a result of mud weight increases to overcome troublesome formation overpressures and associated High Pressure Low Volume (HPLV) nuisance gas. Without increasing mud weight to control overpressures, MPD technology was applied to safely and cost effectively drill through overpressures and avoid an intermediate casing string normally used to isolate a loss zone. MPD trial results examined in this paper addresses many of the issues and provides forward-looking statements regarding large-scale introduction of the system to other fields. The multi-well trial results showed a close match to the predicted MPD ROP curve, achieving an economically rewarding ROP gain of at least 2.5 times and gross well cost reductions of over 20%, without recordable troublesome zone Non-Productive Time (NPT). Initial concerns of borehole instabilities using lightweight mud with borehole pressures less than the adjacent pore pressure were not observed (in both vertical and directional well cases). Introduction MPD technology is challenging the traditional drilling practice of weighting a mud system while drilling formation overpressures. MPD practices are suggesting that weighting up of a mud system is a major source of invisible NPT. Non-Productive Time (NPT) It has been reported by Dodson(1) that 25% of an average well's cost is recordable drilling NPT. As such, best practice Operators closely track drilling NPT. NPT is also commonly referred to as drilling flat curve time. Typical recordable NPT categories and key performance indicators used are as follows:Tight HoleDeviation ProblemsTool FailureHole Cleaning IssuesEquipment Failures and DelaysWell ControlLost Circulation Most Drilling Engineers have realized that Drilling Curves are under intense step change demands to reduce the time taken historically to reach a target depth. Tracking of NPT permits quantitative and statistical drilling analysis, to optimize drilling programs, control cost uncertainties (risks) and improve drilling economics. Drilling time is directionally proportional to cost, and in most cases, time saving (over cost) is the primary driver behind optimization strategies. Operators will often accept higher daily costs in order to save overall drilling time.

Drilling operations daily generate large amounts of data but surprisingly, a significant proportion of these data are not utilized in a manner that shortens the learning curve and promotes drilling efficiency. The authors, through this paper, demonstrate how drilling analysis methodology helped identify performance gaps in a West Central Canadian field. The above is captured under the much espoused philosophy characterized by the questions:Where are we now?What is possible?How do we get there? By applying this tool, significant cost savings to the tune of CAD$7.3 mln have been achieved as at the time of preparing this paper. Introduction There have been various approaches developed over the years to optimize the well construction process but only a few of these have addressed the subject of improving drilling performance through a systematic analysis of historical data. The drilling analysis concepts described in a companion paper1 were applied to an already optimized field and additional cost savings of 15% were realized as at the time of preparing this document. The driver to the adoption of drilling analysis as a core requirement was prompted by the requirement to reduce drilling cost as a way of improving project economics in the matured sedimentary basins of Western Canada. At the commencement of drilling analysis in the Wild River Field, a total of 41 gas wells have been drilled by Anadarko and its predecessors since the first well was spudded in 1999. Thirteen of these wells were drilled to between 5 and 20 degrees deviation while the rest were drilled as vertical wells with maximum allowable deviation of 2 degrees. Hole sizes and casing schemes were largely similar (Fig 1). The surface holes were drilled with 311 mm bits to about 430 m while the production holes were drilled through the reservoir (Cadomin) to TD in the Fernie formation at 3050 m. The wells, from spud to rig release, were initially drilled between 56 and 70 days at the onset of field development, but with more wells drilled, drilling operations time improved and flattened at between 22 and 38 days, averaging 29 days for well depths of approximately 3050 m (Fig 2). The well cost associated with the drilling of these wells also improved from CAD$2.50 - CAD$3.75 mln (in money of the day terms) at the beginning of field development to an average of CAD$1.76 mln (or $570/m) before performing drilling analysis. The public domain data from 40 other wells drilled by 4 other operators in the Wild River field were also studied and the drilling time results showed similar performance level as Anadarko's (i.e spud to rig release time of 30 days, Fig A-1).

This paper discusses a segment of drilling engineering — drilling analysis — that is assumed to be practiced routinely, but in many cases is not given the necessary attention, time, and resources required. Routinely acquired drilling, geologic, mud-log, and logging data, are shown to be amenable to organization into a knowledge-based structure that permits:Use of statistical analysis to develop challenging but achievable technical limits, or best composite time (BCT), for similar wells - location, depth, hole size.Statistics-based best composite cost (BCC), the dollars equivalent of BCT. Both the BCC and BCT represent practical, challenging but achievable benchmarks that are continuously upgraded, providing significant steps in the process of drilling costs reduction.Specialized learning-curve analysis, trouble-time analysis, flat-time analysis, time vs. depth analysis, cost vs. depth analysis, rig and crew performance evaluation, bit-on-bottom and tripping analysis, time distribution plots, etc.Convenient drilling data cross-correlation with wireline logs, geology and mud-log data, to further delineate drilling problem zones and improve drillingoperational performance.A historical understanding of well construction that can contribute to continuing drilling improvement, and a method to provide feedback and collaboration with company drilling personnel, rig contractors, and service companies. This paper reviews existing variations, key elements, and typical field applications of drilling analysis, and puts forth the case that drilling analysis should become an integral part of drilling engineering, the same way well-test analysis is an integral part of reservoir engineering. The need for a university curriculum and training on this key discipline is stressed, along with the necessity for management to champion the use of drilling analysis as an on-going process to improve organizational drilling performance. Introduction Despite the capital intensive nature of drilling operations, especially offshore where a single well can cost $50-80 million or more, drilling analysis as a core sub-discipline of drilling engineering is not routinely practiced as it should be. This is understandable since drilling engineers are principally rewarded for well planning, (including AFE generation), and well-construction management. Implicit in this assumption is the notion that somewhere in the planning process, there was adequate and appropriate drilling analysis to aid the overall drilling process. With a few exceptions, given the daily pressures and responsibilities of engineers in well planning and drilling operations, this is not always the case. The lack of an organized knowledge-based data-management system that can seamlessly cross-correlate relevant drilling and geologic parameters is another deterrent to drilling analysis not being an integral part of drilling engineering. A literature search with the keywords "drilling analysis" reveals a scant amount of published works, even though several papers have addressed one form or another of what could be classified as drilling analysis (Fig. 1). Over the past thirty years, disciplines such as reservoir engineering evolved specialty skills and systems for pressure transient analysis, and production technologists developed skills and systems for nodal analysis. Clearly both sub-disciplines have greatly contributed to their respective technologies. Yet drilling engineering, to our knowledge, has not formalized tools and processes that would unambiguously constitute drilling analysis. Recently, there has been a formalized company initiative to develop such drilling analysis methodology and tools, with encouraging results. This paper presents some of the key processes, tools, and select field applications. Savings from dedicated applications of these concepts have already resulted in noticeable drilling cost reductions in some areas as shown in a companion paper (Ref. 1).

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractWithin a climate of increasing oil and gas prices, drilling has been caught in a cycle of new, more expensive technology and increasing service and commodity prices. In order to maintain cost effective drilling excellence, Anadarko Canada Corporation's drilling department has developed a multifaceted approach with three major components; pre and postdrill analysis, collaboration and technology. While these three components are commonly part of any current drilling operation, the rigorous approach ACC has applied continues to generate uncommon results in both in-fill and more technically challenging, poorly delineated drilling fields in Western Canada. Our approach and the results generated in two distinct areas of operation are outlined here.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractWithin a climate of increasing oil and gas prices, drilling has been caught in a cycle of new, more expensive technology and increasing service and commodity prices. In order to maintain cost effective drilling excellence, Anadarko Canada Corporation's drilling department has developed a multifaceted approach with three major components; pre and postdrill analysis, collaboration and technology. While these three components are commonly part of any current drilling operation, the rigorous approach ACC has applied continues to generate uncommon results in both in-fill and more technically challenging, poorly delineated drilling fields in Western Canada. Our approach and the results generated in two distinct areas of operation are outlined here.