On average each well within the Barnett Shale play will produce from five (5) to ten (10) horizontal zones. Each zone is perforated and fractured with between 500,000 and 1,000,000 gallons of slickwater prior to isolation in order to repeat the process on the next zone. Previous to the methodology further described within this paper, the composite material frac plugs were deployed into the horizontal section of the wellbore by means of electric wireline and a tractoring system. While proving successful, this system did have limitations with respect to time and ultimately economics especially considering the average number of zones per well that required temporary isolation. This paper will describe a system method improvement being utilized by most operators in the play whereby a Hydraulic Pump-Down Frac Plug is utilized. This cased hole temporary plug can be ‘displaced’ into the well at speeds of up to 200 feet-per-minute with surface pump rates of less than 10 barrels-per-minute. The BHA that is run consists of the Hydraulic Pump-Down Frac Plug, Wireline Adapter Kit, Wireline Pressure Setting Assembly, 2 sets of perforating guns and a firing head. After successful isolation and fracturing, the plugs are removed from the well bore in an under balanced environment by means of a coiled tubing milling assembly. The plugs have also been removed by reversing units utilizing 2–7/8″ tubing and a 4–3/4″ 5-bladed concave mill. This paper will show how the development and use of this methodology has greatly increased the efficiency of completions within the Barnett Shale play by a potential reduction in time of 50% depending on the zone depth. The client costs have been significantly reduced not just in terms of time savings but also when the removal of the requirement for electric wireline with tractoring systems is taken into account. Located in North Texas, (see Figure 1) the Barnett Shale is a massive gas field with one trillion cubic feet of natural gas every seven square miles. It has taken the Barnett Shale many years to become a viable economic proposition. However, through the progress of technology and the determination of reservoir engineers, the Barnett Shale has become a very successful gas play that is still in the early stages of its life cycle. 1 The Barnett Shale is currently producing approximately 1bcf/day of gas with well completions at approximately 1.5/day. Currently, the most active area in the Barnett Shale is the Newark East Field with more than 2,340 wells producing at depths as shallow as 6,500 ft.2
fax 01-972-952-9435. AbstractMetal-to-metal sealing technology is an innovative type of medium to high expansion seal that uses compliant metal as a pressure barrier and incorporates an extraordinary seal performance envelope that cannot be achieved by conventional elastomeric seals. Zonal isolation tools, including bridge plugs and straddle systems, using metal-to-metal sealing technology in place of conventional elastomers may radically challenge existing engineering philosophies by providing a pressure sealing system capable of exceeding the limitations of other existing sealing technologies and eliminating many traditional elastomeric failure modes.The metal-to-metal seal has the potential to change the way downhole equipment provides pressure integrity during pressure pumping operations by utilizing a controlled application of load to expand the metal seal to achieve a fully formed pressure barrier which allows for the metal-to-metal seal in bores of up to 160% of the original seal diameter.In the well servicing market, recent applications of the metal-to-metal seal and the latest lab testing have suggested the prospective of the technology for products for not only the conventional markets but also in the hostile HPHT arena. Metal-to-metal sealing technology could make well suspensions and intervention possible in hostile HPHT wells that were previously deemed inoperable by the complete removal of elastomers from the design. Demonstrating versatility in applications on land to deepwater locations, metal-to-metal sealing devices can be easily deployed on slickline, electric wireline, coiled tubing, or drill pipe to save operator rig time in areas where cost savings are critical.Case studies of the high performance characteristics of the metal-to-metal sealing technology in terms of design, testing, and implementation will recognize its alignment in regards to conventional elastomeric sealing technologies as well as high-expansion inflatable technology.
This paper will focus on a project to redevelop a wireline deployable metal-to-metal seal, ISO 14310 VO qualified, retrievable bridge plug system to allow it to be conveyed successfully in a high rate gas well for acid stimulation zonal isolation operations. Functionality of the original system including the plug and hydrostatic setting assembly had previously been tested in a fluid environment yet envisioned for a gas well application. Initial well installations gave results that led to a reconsideration of the forces being generated by the running and pulling tools due to the differences between a gas and a fluid environment and their impact on system reliability and functionality. The paper will discuss some of the problems discovered with the system for this particular application and the system redesign over a one-year period, which included a number of qualification tests performed at near to real well conditions. This discussion will include information on the complexities of performing such tests and the solutions used to develop a successfully qualified "fit-for-purpose" redesign. The paper will conclude with a high-level overview of the system's first deployment in an actual field well application. Introduction In mid 2006, the operator ran a specifically developed high expansion, retrievable, metal-to-metal (MTM) bridge plug on three 7-in. monobore wells to provide mechanical zonal isolation for high rate, multi-stage acid treatments. The acid stimulation objectives in these three wells were fully met and the MTM seal performed to expectations; however, there were significant operational problems related to the plug system. The MTM bridge plug had been selected due to previous operational problems with conventional elastomeric element type retrievable bridge plugs as well as a number of advantages that the technology presented over these conventional types of plugs for the operator's specific application. Over the course of a year, the system was redesigned to address specific findings from those initial operations. The redesign involved modifications to the plug and the inclusion of additional components and functionality in the running and pulling tools to ensure repeatable system reliability and operability. Final system qualification was extensive and more comprehensive than normally performed for such a system. The redevelopment program and qualification testing demonstrated the importance of testing complete systems at conditions representative of those that would be encountered in actual well operations. Repeat testing was important to establishing system reliability. It also highlighted the need for a project-based approach with clear communication on a regular basis between multi-disciplinary, cross-functional teams. Completion and Reservoir Overview The operator has implemented two different types of big bore wells to deliver high flow rates. The well types are a 7-in. tubing monobore and a 9" x 7"-in. tubing optimized big bore (OBB). They are shown in Fig. 1. The reservoir formations are cased and cemented behind a 7-in. production liner in both types of well. Typical well deviations are approximately 55º. The reservoir formations have significant vertical extent and are initially over-pressured but at moderate temperature. Reservoir pressures may vary between zones and this causes cross flow between completed reservoirs. To produce at the design rates for an extended period, high volume matrix-rate-multi-stage (MRMS) acid stimulations are required. The substantial reservoir heterogeneities combined with the significant vertical extent of the productive zones present extreme challenges for acid treatments for all zones.
Zonal isolation tools, including bridge plugs and straddle systems, using metal-to-metal sealing technology in place of conventional elastomers may radically challenge existing engineering philosophies by providing a pressure sealing system capable of exceeding the limitations of other existing sealing technologies and eliminating many traditional failure modes. Metal-to-metal sealing technology is an innovative type of high expansion seal that uses expanding metal to form a high integrity pressure seal and incorporates an extraordinary seal performance envelope that cannot be achieved by conventional elastomeric seals. The seal design utilizes the controlled application of load to expand the metal seal to achieve a fully formed pressure barrier which allows for the metal-to-metal seal in bores of up to 160% of the original seal diameter. The metal-to-metal seal has the potential to change the way downhole equipment provides pressure integrity in HPHT environments. In the well servicing market, recent applications of the metal-to-metal seal and the latest lab testing have suggested the prospective of the technology for products in the HPHT arena. Metal-to-metal sealing technology could make well suspensions and intervention possible in hostile HPHT wells that were previously deemed inoperable by the complete removal of elastomers from the design. Ideal for HP/HT applications, metal-to-metal sealing devices can be easily deployed on slickline, electric wireline, coiled tubing, or drill pipe to save operator rig time in areas where cost savings are critical. Case studies of the high performance characteristics of the metal-to-metal sealing technology in terms of design, testing, and implementation will recognize the alignment to the increased demands of HP/HT applications. History The high expansion arena for bridging devices was revolutionized in the mid 1980s with the introduction of the inflatable type isolation device. In 1986, inflatable type packers and bridge plugs that could be run on coiled tubing through the production tubing were introduced in Prudhoe Bay, Alaska. The inflatable packers and bridge plugs had improved expansion characteristics dictated by the rigors of going through tubing and setting in the casing below without sacrificing pressure holding capability. By eliminating the workover rig and all ancillary operations required by conventional workovers, through-tubing servicing allowed wells to be returned to production in significantly less time. Inflatable tools have long been valued in completion and workover operations due to their unique ability to expand to several times their diameter and to seal effectively; however, drawbacks to inflatable systems exist in their expansion limitations and differential pressure capabilities at higher temperatures. In spite of these drawbacks, operators value the ability to perform basic remedial operations while not pulling the production tubing string, and continue to utilize the advantages of high expansion inflatable technology in the well serving market.
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThis paper will outline the history, and operation of a Through-Tubing selective injection tool used for the purpose of water shutoffs. This tool is an inflatable, re-settable, coiled tubing-conveyed straddle packer assembly designed to run through production tubing and isolate a portion of perforated, screened, slotted, or open hole allowing precise placement of water blocking chemicals, Acidizing, or chemical fluids.The paper will include a description of 18 field runs of this tool used for water blocking chemicals from 1995 through October 1999 and will examine the 3 case histories listed below in more detail: 1. Through-Tubing selective water shut-off polymer job through casing perforations with a single packer 2. Through-Tubing selective water shut-off polymer job of an intermediate zone in 4.5" casing 3. Through-Tubing selective water shut-off polymer job of an intermediate zone in 3.5" screen linerSpacing of Straddle Packers 49 ft. Figure 134746 ft. 4790 ft.
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