TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe positive economic impact of a metal bearing seal on roller cone bits used in conjunction with downhole motors and steerable systems in a Abu Dhabi Onshore fields has been dramatic. The metal seal has proven its ability to extend seal/bearing life of roller cone bits significantly (one million bit revolutions or 1000 krevs without seal failure are common) relative to elastomer sealed bits. This bearing, along with an improved cutting structure, has resulted in more on bottom drilling time.The metal seal technology is especially useful when used on steerable motor assemblies. The bits have been successfully applied to kick-off from vertical and generally drill the 8-1/2" build section between 8°-14°/100 ft to the landing point at 90°, through interbedded formations ranging from soft shales to medium-hard limestones. Unconfined Compressive Strength varies from 5,000 psi to 15,000 psi. As the bits were applied throughout the region, the manufacturer used step changes to improve the cutting structure and hydraulics to further enhance bit performance and durability.The authors will document significant cost reduction through improved bit performance in high-speed directional applications for the new metal bearing seal design compared to the best performing elastomer sealed bits. The study will include data from 386 bit runs totaling over 232,734 feet and 15,821 drilling hours documenting a decrease of 42% in cost per foot or a saving of US$3,836,400 over a three year period between
This paper describes the successful use of eccentric tools to solve a variety of complex down hole problems associated with drilling through flowing salt formations in the Gulf of Suez. The tool allows simultaneous reaming and drilling with steerable assemblies (SRWD). The SRWD technology was applied in two intervals on well A-19, East Zeit Bay Field, as insurance against hole problems caused on the previous wells by salt mobilization and saltwater flows. On well A-19, the operator had to decide either to drill with a large casing program or use the under reaming technology while still drilling an economic well. Additional problems involved drilling through large salt sections, possible saltwater flows, interbeded hard limestone/anhydrite sections and an aggressive directional wellbore design. Without SRWD technology, the operator would have to drill a well using a large hole design, which was complicated due to the platform considerations, casing inventories available, and the higher costs associated with the increases of mud volumes, and decreased penetrations rates. The operator was able to steer the 14-inch SRWD tool to keep the wellbore on track at 38 degrees to the planned casing point. The lower 12–1/4" build section was drilled from 38 degrees to 67 degrees while turning the hole from an azimuth of 108 degrees to 123 degrees with no major problems associated with the SRWD tools. The authors will discuss the optimization of the well design, the technology of the SRWD and the close cooperation between all the service companies required to help the operator drill the longest horizontal well in the Gulf of Suez without sacrificing cost per foot, and making a successful well. Introduction The East Zeit field, is located in the Gulf of Suez, Egypt, Figure 1. The company has operated the East Zeit field since 1996 and drilled two of the 19 wells (Figure 2) on the platform. The major geologic structures are the same throughout the Gulf of Suez with regards to the Kareem, Nukhul, and the Nubia formations as depicted in a generalized stratigraphic section, Figure 3. The majority of the production from the 19 wells is from the Nubia and Nukhul formations. The Kareem formation is productive in the area, but had not been drilled due to its limited economic potential near the platform. However, geological mapping indicated economic pay could be located southeast of the platform if drilled horizontally, Figure 4. Challenges The challenge was to drill a commercial horizontal well in the Kareem formation from the East Zeit A Platform starting the horizontal section 5000 ft away from the surface location. Drilling in the East Zeit area had been difficult due to platform constraints, lost circulation problems, saltwater flows, plastic formations, and hard interbeded formations. Additionally, due to the complex regional geology, the well design had to be flexible to allow for directional changes as the well was drilled. Drilling in the Gulf of Suez, Egypt presents operational challenges due to equipment availability and logistics.
The positive economic impact of a metal bearing seal on roller cone bits used in conjunction with downhole motors and steerable systems in a Abu Dhabi Onshore fields has been dramatic. The metal seal has proven its ability to extend seal/bearing life of roller cone bits significantly (one million bit revolutions or 1000 krevs without seal failure are common) relative to elastomer sealed bits. This bearing, along with an improved cutting structure, has resulted in more on bottom drilling time. The metal seal technology is especially useful when used on steerable motor assemblies. The bits have been successfully applied to kick-off from vertical and generally drill the 8-1/2" build section between 8°-14°/100 ft to the landing point at 90°, through interbedded formations ranging from soft shales to medium-hard limestones. Unconfined Compressive Strength varies from 5,000 psi to 15,000 psi. As the bits were applied throughout the region, the manufacturer used step changes to improve the cutting structure and hydraulics to further enhance bit performance and durability. The authors will document significant cost reduction through improved bit performance in high-speed directional applications for the new metal bearing seal design compared to the best performing elastomer sealed bits. The study will include data from 386 bit runs totaling over 232,734 feet and 15,821 drilling hours documenting a decrease of 42% in cost per foot or a saving of US$3,836,400 over a three year period between April 1998 – March 2001. Introduction Historically, elastomer bearing seal (ES) TCI bits were used to drill the 8-1/2" build section of a typical horizontal well drilled in Field A. The lithology consists of interbedded shale and hard limestone. The shale has an unconfined compressive strength (UCS) in the 5,000 psi range and the carbonate section in 15,000 psi range (Figure 1). The rate of penetration in this section is controlled by directional considerations, however the operator felt there was an opportunity for considerable performance improvement. In order to meet client expectations and implement industry best practices, the operator attempted to drill the 8-1/2" build section with a positive displacement motor (PDM) and two different styles of PDC bits. However, due to the soft nature of a shale formation, the first bit type developed excessive reactive torque due to high depth of cut resulting in loss of tool face control. Conversely, the other PDC bit and motor assembly could not build angle as required. Due to these issues with PDC bits, the operator elected to reexamine the preferred IADC Code 517 roller cone bit to achieve the desired performance improvement as well as meet directional requirements. General Well Plan/Profile A description of the two types of well plans and associated directional profile are provided for background information. In general, the 8-1/2" build section is drilled in one of the two following ways. Case One The 12-1/4" vertical hole is drilled and the 9-5/8" casing is set at the top of a massive shale formation. The 8-1/2" section is then drilled through the shale and limestone (reservoir section). The massive shale formation is open. Drilling Fluid Mud used is either an OBM or KCL/BHPA. Two experiments with silicate based fluids appeared to contribute to bit seal failure. Mud weight varies between 80–85 pcf based on formation pressure.
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