The infinite conductivity theory to enhance production was introduced to the industry around 1971. Exploration from the 1970s to the 1990s focused on high permeability formations. The unconventional reservoirs and tight formations were left behind until new technology could enable hydrocarbons to be produced in economical manner. Operators seek methods to both increase initial production and slow the decline rates. This paper describes the infinite conductivity technique to help to enhance production in unconventional reservoirs and tight formations. The advanced pillar fracturing technology was evaluated as an infinite conductivity technique using binding agents to help generate stabilized proppant pillars to create voids and conduits inside the induced fractures during fracture stimulation treatments. The pillars remain stable at reservoir pressure and temperature to help to prevent excessive fracture closure during drawdown. The methodology uses specific surface equipment designed to establish pulsing of slurry and clean fluid segments during proppant placement. This methodology is combined with liquid resin technology to help to prevent proppant and fines migration, as well as reduce proppant embedment that would allow blockage of the conduit spaces. Consequently, the new technology reduces the necessary proppant volume pumped into the formation, thereby reducing the potential of proppant screenout. Mechanical stress on the packed fractures is significantly greater during production when drawdown pressures are maximized and reservoir pressures begin to decline. These two pressures can lead to greater stresses on the proppant after closure. High closure stress also applies pressure to the proppant during production; consequently, the proppant has an increased tendency to crush. Proppant diagenesis is possible and can consequently contribute to reductions in conductivity. However, the application of liquid modified resin creates a film on the proppant surface, resulting in significant reductions in proppant reaction with the formation rock and fluid. This technique reduces diagenesis and helps to control fines generated from crushing that could plug the proppant pack and reduce conductivity. Modified liquid resin also increases pillar strength by creating a film on proppant grains. The application of different shear stresses enhances and stabilizes the strength of the pillar and keeps the newly created conduits open to flow. This paper presents a case history that shows that the production from a well stimulated without modified liquid resin declines significantly more than another well treated with resin-coated proppant. This paper presents a novel infinite conductivity technique that uses a pulsed proppant fracturing process to provide enhanced and sustained production over conventional treatments. The proppant pulsing process helps to create proppant pillars with open flow paths that are highly conductive and can enable almost infinite conductivity.
Hydraulic fracturing for well performance optimization has been implemented for many years in BRN field in north-eastern part of Algeria, operated by Groupement Sonatrach-Agip (a JV between ENI and Sonatrach). Because of unfavorable petro-physical properties of the reservoir, some challenges have been encountered in avoiding any additional damage to the fracture faces and to facilitate the post-job treating fluids flowback. Effective fracturing treatment designs should consider preventive actions for possible fracture conductivity impairment, such as damage attributed to stress, proppant embedment, and damage caused by fracturing fluid residues. Correct proppant selection can minimize effects from stress and embedment, while a suitable fluid system can minimize conductivity impairment from gelling agent solid residue. Traditional guar-based fluid systems, which are often a preferred choice in the industry for fracturing operations, can have damaging effects on fracture conductivity attributed to inherent insoluble residue that can plug proppant pack pore spaces. Implementing a less damaging fluid system can not only maximize retained conductivity, but furthermore provide longer effective fracture half-lengths which may result in more efficient treatment fluid recovery. Therefore, to overcome such issues, a new fracturing fluid has been developed, leaving little or no residue after breaking. Moreover, this fluid system can be tailored to a wide variety of bottom-hole conditions and has comparable properties to guar-borate fluids with respect to proppant transport capacity and rheological characteristics (e.g. viscosity building and breaking behaviors). This paper presents the first successful implementation of this novel fluid system in the BRN field in Algeria for improving the water injection performance of a well characterized by a tight sandstone reservoir. Field data collected after performing the propped fracturing treatment confirm the effectiveness of the fracturing fluid design. Specifically, the following topics will be extensively described within this paper: Characteristics of the BRN field and history of conventional guar-base fluid systems used previously within this field;Specifics of the near residue free fluid system (cross-linker types, pH requirements, etc.);Design considerations for the implementation in the BRN field of this novel fracturing fluid;Results of post fracturing water injection performances.
Rhourde Attar field in the northwestern Algerian desert is exploited from the Lower Devonian sandstone. This formation is composed of sandy and silty-sandy intervals with thin, shaly intercalations. The reservoir is characterized by very porous sands (20 to 25%), which also show relatively low permeability (1 to 15 md). Deposition of chamosite minerals reduced permeability, without reducing primary porous volume. This paper proposes a pillar fracturing technique designed to overcome formation constraints and enhance production. Beyond the moderate petrophysical properties related to rock diagenetic history, the reservoir is suffering from a gradual depletion trend, limiting the oil production rate and driving the bottomhole operating condition below the bubble point. It was proposed that placing a highly conductive fracture stimulation treatment could possibly help overcome these constraints. An oil producer well of the field was selected for the first application of a pillar fracturing technique combined with a resin to consolidate the created channels within the fracture. The pillar fracturing technique allows conductivity maximization through the placement of open channels within the stabilized proppant pillars. This unique fracture geometry is achieved by pulsing clean fracturing fluid stages alternated with slurry stages that carry the propping agent. The proppant pillars are then stabilized with the addition of a specifically designed resin to coat the proppant as it was being pumped throughout the entire fracturing process. Proper candidate selection, accurate fracture modeling, and employment of proven pumping equipment are crucial elements for achieving a successful and safe intervention. The implementation of this stimulation technique provided positive results both in terms of operational execution and final well performance. Additionally, this technique mitigates the risk of undesired screenout by reducing the proppant volume compared to a conventional job. Moreover, the initial production of the well revealed a significant improvement while the long-term performance showed a stabilized trend. Based on these outcomes, the use of this technique could face a fast increase within the Algerian market, considering also possible refracturing interventions on older wells.
The Lower Triassic Montney Formation produces from the Western Canadian Sedimentary Basin. This shale play is extensive as it covers nearly 57,000 square miles. The play consists of landing intervals in the Lower, Middle, and Upper Montney Formation for which the oil and gas industry uses multiple fractured horizontal well completions to recover natural gas. Both cased and open hole completions are utilized in the Montney Formation. Identifying the key drivers for success of multiple fractured horizontal wells is not straightforward, especially in unconventional reservoirs like the Montney. One study by Christie et al investigated the completion trends of four Montney operators since 2005 and showed the average completion interval length, the average number of fracture stages, and the volume of proppant used per fracture all increased over time. Al-Alwani et al, provided a statistical analysis of both open and cased hole Montney completions based on publically available data. The authors showed that for the entire well population, cumulative gas recovery per stage declines as the number of completed stages increased. It was also shown that cased hole wells performed much better than open hole wells although the completion costs were at least 50% greater. However, this statistical analysis did not differentiate between completions in the Upper, Middle, or Lower Montney nor did it include perforation cluster data. This work documents the statistical analysis of 296 cased-hole horizontal gas well completions in the Upper and Lower Montney. The work extends the previous statistical study of Montney completions by focusing on cased hole completions, including completion cluster information, and examining the performance of Upper and Lower Montney completions separately. Results of this analysis show that cumulative gas production per cluster decreases as more perforation clusters are placed in both the Upper and Lower Montney. The study demonstrates that the cumulative gas production per cluster and initial gas production (IP) is higher for the Upper Montney Formation than the Lower Montney Formation. This work benefits the industry by: Providing a more focused statistical analysis of horizontal gas well cased hole completion performance in the Montney, compared to recent literature documenting industry practices. Identifying a maximum recommended liquid per cluster amount for completions in the Montney Formation. Providing a comparison of Upper and Lower Montney cased hole completion performance.
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