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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.
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 application of modified reaming technology in Mississippi Canyon, deep-water Gulf of Mexico (GOM) has had a beneficial impact on drilling costs. The ability to drill cement and associated downhole float equipment with steerable ream while drilling (DOSRWD) tools has become increasing important in deep-water GOM drilling. The extra trip required by conventional bi-center and eccentric tools adds costly "flat" time to a well's drilling program. Additional improvements in the eccentric bit's geometry and cutting structures has reduced the number of trips and significantly lowered drilling costs. Traditionally, when a ream while drilling system was used, the operator drilled the cement and float equipment with a pass through size bit, then tripped out of the hole to pick up the ream while drilling bottom hole assembly. For example, float equipment and cement in 9–5/8" 53.5# casing was drilled out with an 8–1/2" bit. A trip was then made to pick up a standard 9–7/8" SRWD bottom hole assembly. The DOSRWD's ability to drill cement and float equipment inside casing and then continue drilling ahead, plus the option to use either a tricone or PDC pilot bit depending on directional requirements and formation type make it the appropriate tool for the application. Water-based fluids are preferred in the upper hole section while synthetic mud is used deep in the wellbore. Because of balling concerns in WBM and stringent directional requirements, the operator utilizes metal bearing seal steel tooth pilot bits in most cases (IADC 117). The authors will document rig cost savings ranging from US$40,000 to $105,000 per trip in some applications with total savings exceeding US$388,000 in some instances. Introduction Mississippi Canyon (MC) Blocks 667, 711, and 755 are located 150 miles south of New Orleans, Louisiana in approximately 3000 ft of water. These blocks are considered deep water Gulf of Mexico and pose numerous drilling challenges to the operator.The well plan calls for a relatively large wellbore to be drilled through the reservoir sand to accommodate high flow-rate completions. To successfully penetrate overburden with high pore pressure, the operator has used several hole-opening systems in the area to drill an oversized hole in order to accommodate multiple casing strings in the upper well sections (Figure 1). If not for the narrow margin between pore pressure and fracture gradient in the area, the operator could have achieved borehole diameter requirements through the reservoir sand with a conventional casing design. To date, a total of six wells have been drilled in the aforementioned blocks. All but one of the wells has been directional in nature. Directional well profiles have been either build-hold or build-hold and drop (S shaped wells). The angle build portion of the wells usually takes place in the upper well sections (4000-ft to 5000 ft TVD). Two hole opening systems have been utilized to drill these upper hole sections:The borehole is drilled conventionally and then opened with an underreamer (i.e. drill a 14.75" hole to casing depth then open the hole with a 17" underreamer to set 13.375" casing.The hole is drilled with a 17" steerable ream while drilling system (SRWD). In MC Blocks 667, 711, and 755, formation above the producing horizon consist of gumbo, unconsolidated sand and sticky shales. The unconfined compressive strength of the gumbo and shales is usually below 1500 psi in the upper sections. Although the formation becomes harder at depth, the unconfined compressive strengths of both the shales and sands rarely exceeds 3500 psi (Figures 2 & 3).
A detailed test program was performed with an eccentric tool at the Baker Hughes Experimental Test Area (BETA) field research facility to evaluate the feasibility of its use in an Expandable Tubular Technology application in the North Sea. The testing used a 9–7/8" Drill Out Steerable Ream While Drilling (DOSRWD) tool in conjunction with 6–1/2" pilot bits (both PDC and roller cone). Motor bent housing settings included 1.0°, 1.5°, 1.75° and 2.0° bends to evaluate directional and stability response. Surface speeds were varied from 0, 35, 50 and 75 rpm at each motor housing setting. Caliper logs including four and six-arm and ultrasonic borehole imaging (UBI) tools were used to characterize the borehole under all conditions. The analysis included directional tendencies, down hole vibration monitoring and borehole diameter, quality and degradation over time. The test results show the 9–7/8" DOSRWD system is capable of providing the high quality wellbore required for expandable tubular technology, ensuring the casing can be run, expanded and isolated across the formation. Introduction Expandable tubular technology has the potential to significantly reduce well construction costs. Conventional well construction results in telescoping of the well size from the wellhead down to the reservoir. Apart from resulting in large expensive surface casing, wellheads, trees and operating equipment, the method can result in an unworkable small hole size at the required depth. This could then lead to compromises in well operability or in worst case failure to reach the final objective. Expandable tubulars can help solve difficult drilling challenges posed by high-pressure zones, deepwater environments and troublesome sub-salt plays.1,2,3,4,5 Its innovative characteristics allow operators to explore in remote geologic regions and exploit reserves once considered unprofitable if drilled with conventional technology. Instead of using progressively smaller diameter pipe as drilling progresses deeper, Expandable Tubular Technology allows tubular diameters to be expanded with specially designed "pigs," or mandrels. This reduces well tapering while preserving borehole size. Expandable technology can also extend the profitable life of mature fields by internally cladding existing wellbores to isolate troublesome zones. This developing technology has created a need for improved understanding of the directional tendencies of eccentric drilling tools run on steerable assemblies and the wellbore geometry and quality that can be achieved with these tools. Consistent wellbore diameter is of particular concern for expandable tubulars. If the wellbore diameter is too small, expansion of the pipe with a fixed diameter cone might not proceed properly across sections of firm formation. Worse yet, the expansion cone could become stuck requiring remediation or sidetrack of the well. A wellbore that is too large could affect the sealing effectiveness depending on the sealing system used. For example, a closer diameter tolerance would be required if the seal mechanism is an integral part of the casing (elastomer bonded to the outside of the casing).
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