The completion cycle for the development of unconventional resource plays, such as the Eagle Ford shale in South Texas, requires multiple hydraulic fracture stages to be placed in the horizontal section of the wellbore to effectively stimulate the reservoir. Inefficiencies in the completion design caused by conventional "plug-and-perf" (P-n-P) methodologies can increase the costs associated with the delivery of hydraulic fracturing. However, new methodologies have recently been developed to mimic the P-n-P process that allow the operator to fracture stimulate the reservoir in a more economic and time-efficient manner. The Eagle Ford shale in Lavaca/Gonzales Counties, Texas is similar to many high-carbonate-content oil shale formations. In South Texas, the industry has a preference for cementing the lateral section for fracture stage isolation. This case study explores the successful implementation of a cemented multientry point sliding sleeve technology (CMEPT) in the Eagle Ford shale. The combination of these technologies was the first ever of its kind. This study also illustrates some of the lessons learned during the years of development of this integrated service technology. This paper highlights the key well that successfully implemented these technologies. The Kudu Hunter No. 1H well was drilled to a measured depth of 16,302 ft with a lateral length of over 6,000 ft. The integrated service design proposed a hybrid completion design with 2,000 ft of lateral completed by means of a nine-stage CMEPT and the remaining 4,000 ft of lateral completion by means of the P-n-P method. The CMEPT allowed the placement of ~1,840,000 lbm of premium white sand with surface modification agent (SMA) by means of 1,740,000 gal of guar-based hybrid fluid over nine stages in 22 hr, and the remaining 11 stages of P-n-P completion placed ~2,310,000 lbm of premium white sand and SMA by means of 1,940,000 gal of guar-based hybrid fluid in ~80 hr. The stand-alone conventional P-n-P process has become a barrier to the economic delivery of fracture stimulation. This case study illustrates how the adoption of the CMEPT integrated service process provides efficiencies in the completion cycle and maximizes stimulated reservoir volume (SRV) along the well path.

Shale and unconventional reservoir wells require multiple completion options be available so that the best one can be selected to maximize the stimulation influence potential, enable efficient operations, and increase production potential. Shale and unconventional reservoir continuous resource wells are typically drilled horizontally with the completion system run in the lateral section of the wellbore. The completion design must enable the hydraulic fracturing of multiple discreet treatment zones in the target interval to help ensure economical production. Traditionally, unconventional reservoir wells have been completed using a plug and perforate methodology. This completion uses wireline intervention to set composite fracturing plugs for stage isolation and to perforate individual stages. Due to inefficiencies with this type of completion design, single entry fracturing sleeve systems (SE FSS) completions have gained acceptance. SE FSS offer a single entry point per stage and remove the need for wireline intervention thereby increasing completion efficiency. Recently, multi-entry fracturing sleeve systems (ME FSS) completions have been deployed in unconventional reservoir stimulation operations. ME FSS completions also do not require wireline intervention, and allow for multiple entry points per stage to be simultaneously stimulated. Even though it is optimal for unconventional reservoir development to have several completion alternatives, evaluation of the best method can be challenging. This paper will evaluate the three dominant and currently applied completion methods by comparing wells in the Middle Bakken continuous resource play which have utilized all identified systems. The paper will discuss each of the three completion methods (Plug-and-Perforate, SE FSS, ME FSS), the completion design, and fracturing operations that are executed. The paper will then illustrate production results from using all three of the completion methods. This data will be drawn from similar well designs for comparison purposes. Assessment of viability and production efficiency of ME FSS completions against other completion methods is the primary focus. Results will be presented based on production outputs obtained after a qualified 180 day period. Conclusions will also highlight the potential efficiency gains of a ME FSS completion versus traditional methods.

Horizontal shale completions require multi-stage high-pressure hydraulic fracturing stimulation treatments in order to deliver commercially viable production in low permeability reservoirs. Unconventional shale plays, such as the Eagle Ford and Haynesville Shale, often can require stimulation treatments that must be implemented in high pressure and high temperature (HPHT) conditions. Typically, these wells are completed with long casing strings, and it is critical that these monobore casing strings withstand high injection pressures as well as maintain mechanical integrity during thermal contraction/expansion. So what happens when the pre-frac casing pressure integrity pressure test fails? What is the "fix" that will allow treatments to be pumped at high pressure and rate? How will frac stages be isolated during the completion? Typically, remediation techniques have included everything from casing patches and expandable casing to coiled tubing completions. Unfortunately, these solutions can have pressure limitations, and in addition, can be cost prohibitive. The authors of this paper will discuss how design of a 4-in. tie-back string with flush joint connections equal to the properties of the casing was capable of repairing a 5-1/2-in. monobore production casing that experienced extensive casing failure. The extremely small annular tolerance did not allow a conventional packer assembly or cementing for pressure isolation; thus, swellable packer technology was used to anchor the casing in place. A special flow-thru frac plug was designed so that it could be pumped through the 4-in. tie-back casing and set in the 4-1/2-in. lateral, allowing a plug-and-perf fracture completion to be performed. The stimulation treatments were pumped to completion and demonstrated 1), that the pressure isolation integrity of the casing system was satisfactory; and 2), that the flow-thru frac plugs could maintain isolation between stimulation treatments. This wellbore was in the Eagle Ford Shale. True vertical depth (TVD) was ~ 13,000 ft, bottomhole temperature (BHT) was ~325°F with a 0.95 psi/ft frac gradient, and surface pressures exceeded 10,000 psi during the stimulation treatments.

Horizontal shale completions require multistage high-pressure hydraulic-fracturing stimulation treatments to deliver commercially viable production in low-permeability reservoirs. Unconventional shale plays, such as the Eagle Ford shale and Haynesville shale, often can require stimulation treatments that must be implemented in high-pressure, high-temperature (HP/HT) conditions. Typically, these wells are completed with long casing strings, and it is critical that these monobore casing strings withstand high injection pressures as well as maintain mechanical integrity during thermal contraction/expansion. So, what happens when the prefracturing casing-pressure-integrity pressure test fails? What is the "fix" that will allow treatments to be pumped at high pressure and rate? How will fracturing stages be isolated during the completion? Typically, remediation techniques have included everything from casing patches and expandable casing to coiled-tubing completions. Unfortunately, these solutions can have pressure limitations and can also be expensive.The authors of this paper will discuss how design of a 4-in. tieback string with flush joint connections equal to the properties of the casing was capable of repairing a 5 1 =2-in. monobore production casing that experienced extensive casing failure. The extremely small annular tolerance did not allow a conventional packer assembly or cementing for pressure isolation; thus, swellable-packer technology was used to anchor the casing in place. A special flow-through fracturing plug was designed so that it could be pumped through the 4-in. tieback casing and set in the 4 1 =2-in. lateral, allowing a plug-and-perforate fracture completion to be performed. The stimulation treatments were pumped to completion and demonstrated that the pressure isolation integrity of the casing system was satisfactory and that the flow-through fracturing plugs could maintain isolation between stimulation treatments. This wellbore was in the Eagle Ford shale. True vertical depth was approximately 13,000 ft, bottomhole temperature was approximately 325 F with a 0.95-psi/ft fracture gradient, and surface pressures exceeded 10,000 psi during the stimulation treatments.

Development of unconventional resource plays traditionally were completed using the "plug and perforate" the method (plug-n-perf). In recent years, however, multi-stage fracturing sleeves have seen growing industry acceptance as an alternative completion method to plug-n-perf and is now being employed with increasing frequency with both cement and openhole isolation methods in unconventional resource plays. This type of system is operated by dropping a ball from the surface that seats in a landing baffle to actuate the sleeve and allow for fracturing of the formation. These balls and baffles often can be removed from the ID of the casing string by milling, post frac to remove possible restrictions. However, there are situations that can affect the successful milling of the balls and baffles. This paper explores the conditions that can affect the ball and baffle millout process of multi-stage fracturing sleeves. Different aspects of the milling process will be reviewed to determine the critical elements that must be taken into consideration when milling the balls and baffles. Specific factors include multi-stage fracturing sleeve dimensions, wellbore trajectory, torque and drag, depth location, mill design, weight-on-bit (WOB), viscous pill sweep frequency, and other milling procedures. The investigation of the millout of 185 multi-stage fracturing sleeves in Eagle Ford Shale well completions will analyze these factors, which then will be contrasted with surface millout testing on over 100 multi-stage fracturing sleeves performed on a custom millout testing machine. The surface testing allowed visual observation of millout processes and real-time changing of millout variables that reduced risk and lowered operating cost. Both sets of data will then be analyzed to illustrate the critical factors for successful millout operations and discuss the solutions to the millout challenges.