Field Case Studies of Completion Fluids to Enhance Oil and Gas Production in Depleted Unconventional Reservoirs
- John Thomas Pursley (CESI Chemical) | Glenn S. Penny (CESI Chemical) | John H. Benton (Whiting Oil & Gas Corp) | David Terrell Greene (Enerplus Resources USA Corp) | Gary Scott Nordlander (Whiting Petroleum Corp.) | Michael Alan McDougall (Quantum Resources Management) | James W. Crafton (Performance Sciences, Inc.)
- Document ID
- Society of Petroleum Engineers
- Rocky Mountain Oil & Gas Technology Symposium, 16-18 April, Denver, Colorado, U.S.A.
- Publication Date
- Document Type
- Conference Paper
- 2007. Society of Petroleum Engineers
- 3.1 Artificial Lift Systems, 4.2 Pipelines, Flowlines and Risers, 4.6 Natural Gas, 5.2.1 Phase Behavior and PVT Measurements, 5.6.4 Drillstem/Well Testing, 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation, 5.4.10 Microbial Methods, 4.1.2 Separation and Treating, 1.8.5 Phase Trapping, 2.2.2 Perforating, 1.8 Formation Damage, 2 Well Completion, 2.7.1 Completion Fluids, 1.6 Drilling Operations, 5.8.2 Shale Gas, 2.5.2 Fracturing Materials (Fluids, Proppant)
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A study of completion techniques in depleted/low pressure tight permeability gas/oil reservoirs shows great promise through the use of a microemulsion (ME) additive in energized fracture stimulation treatment of new infill wells. This paper presents a comparison of four (4) wells completed according to historical stimulation practices and two (2) wells completed with microemulsion additive. See Table 1 for baseline data.
The damage mechanisms from past practices were exacerbated by depleted/ low bottom-hole pressures, high water saturations, and low bubble point crude. The use of the microemulsion additive reduced the liquid load and promoted liquid recovery, enabling the base fluid gases to establish gas saturated pathways and promote the production of the natural solution gas that is the field's primary economic resource. CO2 is thought to enhance this process by promoting the reduction of the near fracture face oil saturation. The microemulsion potentially enhances this action by reducing the mobility contrast between introduced fluids and reservoir oil, water, and gas phases.
Analysis of the production histories shows that the microemulsion additive significantly enhanced the reservoir conductivity and effective fracture length when compared to the historical completions when in sustained production. The two wells treated with microemulsion additive also experienced less damage as a consequence of the long shut-ins prior to sustained production, than did those with historical completions, which had much shorter shut-ins.
Many drilling and fracturing treatments recover less than half of the injected fluid even with the application of surfactants. It must be assumed that these large quantities of fluid are trapped in the reservoir surrounding the wellbore and in the case of hydraulic fracturing the fluid is trapped in the area surrounding the fracture and within the fracture itself. This trapped fluid has a detrimental effect on the relative permeability, effective flow area and effective frac lengths and without question impairs well productivity. Energized fluids are commonly used in low pressure wells to aid in cleaning up the wells after stimulation. This is particularly true in low perm unconventional fields such as the Signal Peak field in west Texas. This work reviews some of the various techniques that have been used to improve the cleanup of Signal Peak wells with case studies employing various foams, solvents, surfactants and microemulsion technology.
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