Search citation statements
Paper Sections
Citation Types
Year Published
Publication Types
Relationship
Authors
Journals
The problematic drilling environment of soft, balling, and swelling formations that are common in the Elk Hills Field of California required a novel design for the eccentric bits used for the hole-enlargement procedures. This new eccentric bit design met and exceeded the drilling requirements with an improved overall drilling performance of 32% increased penetration rate on average, reduced bottomhole assembly (BHA) damage through enhanced downhole tool life, and improved drilling curve cost benefits. The design also achieved the world record for the operator for the most footage drilled in 24 hours. This was achieved through better directional control, reduced bit balling, and reduced non productive time (NPT) due to an improved BHA design that mitigates the described drilling issues. Given the directional and drilling application, the task was to create an eccentric hole-opening tool capable of superior directional control and cleaning capability in soft formations with known positive displacement motor (PDM) limitations. This required revisiting existing eccentric hole-enlargement requirements, including bi-center and two-piece eccentric technology, and implementing improved drilling features for increased performance. A value-driven tool was designed for use with motor applications in swelling formations. This assembly would meet and exceed the drilling requirements for the field. The authors of this paper will review and discuss the design, development, and run history of this new eccentric bit and hole-enlargement tool. Run data performance improvements, time savings, and reduced BHA damage of existing one-piece and two-piece eccentric tools will be identified and compared with the performance of offset data for bi-center bits and two-piece eccentric tools. The application benefits discussed will include improved directional control, enhanced cleaning effectiveness, and enhanced pilot bit and hole-enlargement tool blade designs compared with that of current bi-center bits for this type of drilling environment. Introduction Ten years ago the operator began drilling the shallow oil zones (SOZ) in the Elk Hills Field in Kern County, west of Bakersfield, California (Fig. 1). The geological zones drilled are of Pleistocene, Pliocene, and Miocene ages, consisting of the Tulare, San Joaquin, Etchegoin, and Monterey formations. Many of the shales in this sequence are time and water sensitive due to a 10 to 35% illite/smectite clay content; hence, it is difficult to maintain gauge hole due to swelling from the water-based drilling fluid. In addition to the shallow wells, deeper wells were drilled through the Stevens sandstone (Fig. 2). Because of the formation swelling, extensive backreaming and time were required to wipe the hole when using standard roller cone bits. Thus, eccentric technology using polycrystalline diamond compact (PDC) cutters was introduced, thereby reducing the number of wiper trips required. By eliminating wiper trips, the cost per foot was reduced by up to 42%. These savings were a direct result of the use of a new one-piece eccentric bit developed to work with a PDM in the soft formations while drilling vertically to a prescribed kick-off point and then building to high angles.
The problematic drilling environment of soft, balling, and swelling formations that are common in the Elk Hills Field of California required a novel design for the eccentric bits used for the hole-enlargement procedures. This new eccentric bit design met and exceeded the drilling requirements with an improved overall drilling performance of 32% increased penetration rate on average, reduced bottomhole assembly (BHA) damage through enhanced downhole tool life, and improved drilling curve cost benefits. The design also achieved the world record for the operator for the most footage drilled in 24 hours. This was achieved through better directional control, reduced bit balling, and reduced non productive time (NPT) due to an improved BHA design that mitigates the described drilling issues. Given the directional and drilling application, the task was to create an eccentric hole-opening tool capable of superior directional control and cleaning capability in soft formations with known positive displacement motor (PDM) limitations. This required revisiting existing eccentric hole-enlargement requirements, including bi-center and two-piece eccentric technology, and implementing improved drilling features for increased performance. A value-driven tool was designed for use with motor applications in swelling formations. This assembly would meet and exceed the drilling requirements for the field. The authors of this paper will review and discuss the design, development, and run history of this new eccentric bit and hole-enlargement tool. Run data performance improvements, time savings, and reduced BHA damage of existing one-piece and two-piece eccentric tools will be identified and compared with the performance of offset data for bi-center bits and two-piece eccentric tools. The application benefits discussed will include improved directional control, enhanced cleaning effectiveness, and enhanced pilot bit and hole-enlargement tool blade designs compared with that of current bi-center bits for this type of drilling environment. Introduction Ten years ago the operator began drilling the shallow oil zones (SOZ) in the Elk Hills Field in Kern County, west of Bakersfield, California (Fig. 1). The geological zones drilled are of Pleistocene, Pliocene, and Miocene ages, consisting of the Tulare, San Joaquin, Etchegoin, and Monterey formations. Many of the shales in this sequence are time and water sensitive due to a 10 to 35% illite/smectite clay content; hence, it is difficult to maintain gauge hole due to swelling from the water-based drilling fluid. In addition to the shallow wells, deeper wells were drilled through the Stevens sandstone (Fig. 2). Because of the formation swelling, extensive backreaming and time were required to wipe the hole when using standard roller cone bits. Thus, eccentric technology using polycrystalline diamond compact (PDC) cutters was introduced, thereby reducing the number of wiper trips required. By eliminating wiper trips, the cost per foot was reduced by up to 42%. These savings were a direct result of the use of a new one-piece eccentric bit developed to work with a PDM in the soft formations while drilling vertically to a prescribed kick-off point and then building to high angles.
Operation of a mature pool requires increasing cost control and infrastructure optimization and consolidation to maintain profitability. The decision to initiate this type of reservoir management plan, sometimes described as harvest, is driven in part by reservoir performance analysis and in part by commodity prices at the time the decision is made. The impact is not limited to operating cost; it can affect reservoir performance itself and the ultimate recovery of reserves. This paper presents the account of a 3.7 TCF sour gas pool in Alberta, Canada and the technical impact of harvest on field operations, reservoir performance and ultimate recovery. The combination of new production decline analysis, well workover with surprising results, and key field observations led to a complete change in reservoir interpretation. A new model emerged where near wellbore regions are deeply damaged and the gas-water contact (GWC) is much lower than expected. Introduction Management of mature pools is not a new challenge. Numerous papers have been written over the years, addressing various technical aspects and aimed at increasing pool longevity1,2,3,4. In the Western Canadian Basin, the surge of exploration and development activity in the 1950's and 1960's has left a legacy of very mature pools with many of these 40 to 50 years old pools still producing today. Alberta Energy and Utilities Board (EUB) records show that of the 30,000 gas pools discovered in Alberta, 2000 or 7% were discovered before 1970. These pools represent in the aggregate 15 TCF of remaining recoverable reserves, as of January 1, 2002, or nearly 40% of the total. Each of these pools was at some point declared mature based on the science of the day and treated as a harvest candidate, i.e. a pool with very limited upside where the best strategy is to control cost and produce what is left without further investment. In some cases this approach becomes a self-fulfilling prophecy. This paper uses the example of the Kaybob South Beaverhill Lake A pool in Alberta, Canada to demonstrate how a large carbonate reservoir can be pulled back from harvest mode to sustained development. First, a history of the main operational activities will be summarized. A description of pool geology and reservoir fluids will be presented next. Operational changes brought about by the perception of the pool as mature will be reviewed and their impact on reservoir surveillance and operation itself will be detailed. Events leading to the change in perception of remaining potential of this pool will be related. The latest drilling activity resulting from this paradigm shift and subsequent production performance will conclude this paper. Pool History The Beaverhill Lake A Pool is a large sour retrograde gas condensate reservoir located in the Kaybob South Field, near the town of Fox Creek, 250 miles northwest of Calgary, Alberta, Canada (Figure 1). It was discovered in 1961 at a depth of 10,500 ft. Initial reservoir pressure was 4722 psia, 1107 psia above dew point pressure. The reservoir is underlain by a large aquifer that has provided pressure support to the Beaverhill Lake A pool and to other hydrocarbon pools in the area. The Beaverhill Lake A pool was divided into three operational units. Kaybob South Beaverhill Lake Units No. 1 and No. 2 (BHL #1 and BHL #2) are operated by one company while another operates Kaybob South Beaverhill Lake Unit No. 3 (BHL #3). Figure 2 illustrates the three production units. Production started in 1968 in BHL #1. Secondary recovery in the form of lean sweet gas cycling was applied immediately to increase recovery of natural gas liquids (NGL) and condensate. Secondary recovery ended with gas blowdown in BHL #1 in 1983. Production started in 1970 and 1972 in BHL #2 and BHL #3 respectively; both switched to gas blowdown in 1990. The decision to proceed with gas blowdown was based upon the maximizing energy recovery given the projections of the time. The action coincided with the onset of low North American natural gas prices, below $2/mcf and an operational switch from sustained development to harvest mode.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.