American Oil & Gas Reporter - December 2011 - 98

SpecialReport: Well Stimulation & Completion Technology
To optimize hydraulic fracture design in the Eagle Ford, one study applied a first-order discrete fracture network (DFN) model to predict fracture geometry. In addition, an approximate analytical production solution for multiple finite conductivity for vertical transverse fractures was used to production history match the well flow streams for DFN calibration and to aid in fracture optimization. Fracture length, conductivity and spacing for multicluster, multistage completions along the horizontal well bore were varied to illustrate the impact of improved hydraulic fracture design on well production and the effect of fracture interference on the resulting geometries and production. The advantage of using a DFN technology for hydraulic fracture design in the Eagle Ford Shale is the ability to model complex fracture behavior that may better predict fracture geometry. The results illustrate the impact of varying fracture/completion design, including the effects of stage and perforation cluster number and spacing, as well as fracture length and proppant pack conductivity for a dry gas well (Well A) and a condensate-rich well (Well B). The treatment and production data, fracture diagnostics and microseismic results provide insights on how sound engineering and fracture modeling can increase recovery and optimize completions in the Eagle Ford play. Fracture Modeling Multiple frac stages and multiple clusters per stage along the length of the horizontal well bore create multiple transverse fractures (perpendicular to the horizontal well bore), which influence both initial production rates and production declines. One of the challenges of fracture modeling in unconventional formations such as the Eagle Ford is that traditional biwing fractures simulators grossly misrepresent actual fracture geometries. Fracture models are an important component of optimizing hydraulic fracture designs for parameters such as fracture conductivity, effective halflength and stage/cluster spacing, but it is critical to recognize this limitation with traditional biwing simulations. Discrete fracture network modeling is one component of a methodology that can be used to improve a completion and stimulation program for enhanced shale production. Well performance can be improved by combining microseismic monitoring, production and radioactive logs, and production history matching with DFN fracture modeling and fracture conductivity enhancement. Economics then can be run to determine net present value and discounted return on investment for various fracture designs and flow streams, leading to improved decision making. The concept of fracture conductivity often is overlooked as a stimulation design variable in shale plays. The presence of nano Darcy rock does not necessarily intuitively lead to the need for higher conductivity. However, while the fracture conductivity required to economically produce a horizontal well in an unconventional reservoir and improve hydrocarbon recovery varies for different shale plays, the primary issue is that many reservoir engineers do not fully appreciate the impact of placing proppant in realistic downhole conditions. The proppant pack conductivity for a selected proppant is a function of particle size, strength, grain shape, embedment into the formation rock, cleanliness/residue of the fracturing fluid, fines migration, closure stress and fluid flow effects. When accounting for these effects, proppant pack conductivity can be reduced by two orders of magnitude. One of the primary reductions is related to nonDarcy and multiphase flow effects, which are well documented in the industry. In addition to
98 THE AMERICAN OIL & GAS REPORTER

these flow effects, incremental reductions for gel damage (even from friction reducers) and proppant embedment can result in fracture conductivity values of 1 to 10 percent of published values. Given the reservoir characteristics for the Eagle Ford formation in both the dry gas and condensate producing wells, ceramic proppants were used in both wells to investigate the impact of higher frac conductivity on productivity. Eagle Ford Geology The Eagle Ford formation is a widespread Upper Cretaceous deposit that has long been known as a source rock for other plays in Texas, yet only recently recognized as an unconventional oil and gas play. In South Texas, the Eagle Ford is between 5,000 and 13,000 feet below the surface with thickness ranging from 50 to 300 feet. The Eagle Ford Shale actually is composed of organic-rich calcareous mudstones and chalks that were deposited during two transgressive sequences: the upper and lower Eagle Ford. The makeup of this rock makes the play significantly different than other unconventional plays such as the Barnett, Haynesville and Marcellus, all of which are found in primarily siliceous environments. The Eagle Ford overlies the Buda Limestone and is deposited as low-angle strata primarily on a gently sloping ramp. The lack of benthic fossils or burrows suggests that the sediments were deposited in an oxygen-deficient basin, which is a necessary condition for preserving organic matter and hydrocarbon formation. The organic richness in the Eagle Ford typically decreases higher in the section, most likely because of a more oxygenated environment at shallower depths. Therefore, the lower Eagle Ford tends to be more organically rich and produces more hydrocarbons. Total organic carbon in the Eagle Ford ranges from 1-7 percent. The Eagle Ford is overlain by the Austin Chalk, which was deposited in shallower water depths, and consequently does not have the same organic-rich qualities. The Austin Chalk does have excellent reservoir characteristics, particularly where it has been fractured, and hydrocarbons found within it are sourced by the Eagle Ford. Because of its widespread regional scale, the Eagle Ford consists of several subplays. In La Salle County, a sweet spot has been identified between the Edwards Shelf edge and the Sligo Shelf edge. The difference in the location of these paleo-shelf edges has effectively created a “minibasin” where the Eagle Ford accumulated in thick deposits in an oxygen-deficient environment. The burial depth in this area (10,000-13,000 feet) has resulted in wells that produce large quantities of dry gas. To the northwest, in the Maverick Basin, the Eagle Ford is much shallower at 5,000-8,500 feet. The Maverick Basin provides an ideal depositional environment for the Eagle Ford, but because of its location further landward on the shelf as well as some uplift from the Chittim Arch, this area did not reach the same level of hydrocarbon maturity as La Salle County. Therefore, it produces a much more condensate-rich gas and potentially volatile oil in the shallowest areas. To the northeast, in Live Oak, Karnes and DeWitt Counties (among others), the Eagle Ford is being explored primarily along the backside of the Edwards Reef. These areas generally produce condensate and gas. More production data and exploration are required to determine the full extent of the Eagle Ford formation, but the results are promising and highlight the reason the Eagle Ford has become one of the most prolific unconventional plays discovered to date.



Table of Contents for the Digital Edition of American Oil & Gas Reporter - December 2011

American Oil and Gas Reporter 12/11
Contents
Reports
Calendar
Oil & Gas Counts
State Legislative
Industry Digest
Tech Connections
Washington Watch
Keystone XL
Liaison Committee
Shale Gas Subcommittee
Endangered Species
Midstream Startups Emerging to Meet Booming Demand
Liquids Resource Plays Have Oil Production Rising Again
Organizers Anticipating Big Things for 2012 PBIOS
Cover Story
R&D Areas Key to Improving Fracturing
Natural Gas Offers Solutions as Transportation Fuel
Completion Design, Frac Modeling Optimize Eagle Ford Wells
Novel Drill-In Fluid Excels in Horizontal ERD Wells
Technologies Optimize Sand Control
Operators Must Manage Risk Before, During and After Drilling
OCS Access: BOEM Offers Business-as-Usual OCS Leasing Plan
Court Finds for Insurers in Gulf Spill Ruling
OIPA
Clean Air Act
IOGA NY
COGA
IPAA Annual
Louisiana
West Virginia
Pennsylvania
Texas
The American Well Servicing Directory, Winter 2011
Industry Focus
Classified Advertising
Advertisers Index
American Oil & Gas Reporter - December 2011 - American Oil and Gas Reporter 12/11
American Oil & Gas Reporter - December 2011 - Cover2
American Oil & Gas Reporter - December 2011 - Contents
American Oil & Gas Reporter - December 2011 - Reports
American Oil & Gas Reporter - December 2011 - 5
American Oil & Gas Reporter - December 2011 - 6
American Oil & Gas Reporter - December 2011 - 7
American Oil & Gas Reporter - December 2011 - Calendar
American Oil & Gas Reporter - December 2011 - 9
American Oil & Gas Reporter - December 2011 - 10
American Oil & Gas Reporter - December 2011 - 11
American Oil & Gas Reporter - December 2011 - Oil & Gas Counts
American Oil & Gas Reporter - December 2011 - 13
American Oil & Gas Reporter - December 2011 - Industry Digest
American Oil & Gas Reporter - December 2011 - 15
American Oil & Gas Reporter - December 2011 - 16
American Oil & Gas Reporter - December 2011 - 17
American Oil & Gas Reporter - December 2011 - 18
American Oil & Gas Reporter - December 2011 - 19
American Oil & Gas Reporter - December 2011 - 20
American Oil & Gas Reporter - December 2011 - 21
American Oil & Gas Reporter - December 2011 - 22
American Oil & Gas Reporter - December 2011 - 23
American Oil & Gas Reporter - December 2011 - 24
American Oil & Gas Reporter - December 2011 - 25
American Oil & Gas Reporter - December 2011 - 26
American Oil & Gas Reporter - December 2011 - 27
American Oil & Gas Reporter - December 2011 - 28
American Oil & Gas Reporter - December 2011 - Tech Connections
American Oil & Gas Reporter - December 2011 - 30
American Oil & Gas Reporter - December 2011 - Washington Watch
American Oil & Gas Reporter - December 2011 - Keystone XL
American Oil & Gas Reporter - December 2011 - 33
American Oil & Gas Reporter - December 2011 - Liaison Committee
American Oil & Gas Reporter - December 2011 - 35
American Oil & Gas Reporter - December 2011 - 36
American Oil & Gas Reporter - December 2011 - 37
American Oil & Gas Reporter - December 2011 - Shale Gas Subcommittee
American Oil & Gas Reporter - December 2011 - 39
American Oil & Gas Reporter - December 2011 - Endangered Species
American Oil & Gas Reporter - December 2011 - 41
American Oil & Gas Reporter - December 2011 - Midstream Startups Emerging to Meet Booming Demand
American Oil & Gas Reporter - December 2011 - 43
American Oil & Gas Reporter - December 2011 - 44
American Oil & Gas Reporter - December 2011 - 45
American Oil & Gas Reporter - December 2011 - 46
American Oil & Gas Reporter - December 2011 - 47
American Oil & Gas Reporter - December 2011 - 48
American Oil & Gas Reporter - December 2011 - 49
American Oil & Gas Reporter - December 2011 - 50
American Oil & Gas Reporter - December 2011 - 51
American Oil & Gas Reporter - December 2011 - 52
American Oil & Gas Reporter - December 2011 - 53
American Oil & Gas Reporter - December 2011 - 54
American Oil & Gas Reporter - December 2011 - 55
American Oil & Gas Reporter - December 2011 - 56
American Oil & Gas Reporter - December 2011 - 57
American Oil & Gas Reporter - December 2011 - Liquids Resource Plays Have Oil Production Rising Again
American Oil & Gas Reporter - December 2011 - 59
American Oil & Gas Reporter - December 2011 - 60
American Oil & Gas Reporter - December 2011 - 61
American Oil & Gas Reporter - December 2011 - 62
American Oil & Gas Reporter - December 2011 - 63
American Oil & Gas Reporter - December 2011 - 64
American Oil & Gas Reporter - December 2011 - 65
American Oil & Gas Reporter - December 2011 - 66
American Oil & Gas Reporter - December 2011 - 67
American Oil & Gas Reporter - December 2011 - 68
American Oil & Gas Reporter - December 2011 - 69
American Oil & Gas Reporter - December 2011 - 70
American Oil & Gas Reporter - December 2011 - 71
American Oil & Gas Reporter - December 2011 - 72
American Oil & Gas Reporter - December 2011 - Organizers Anticipating Big Things for 2012 PBIOS
American Oil & Gas Reporter - December 2011 - Cover Story
American Oil & Gas Reporter - December 2011 - 75
American Oil & Gas Reporter - December 2011 - 76
American Oil & Gas Reporter - December 2011 - 77
American Oil & Gas Reporter - December 2011 - 78
American Oil & Gas Reporter - December 2011 - 79
American Oil & Gas Reporter - December 2011 - 80
American Oil & Gas Reporter - December 2011 - 81
American Oil & Gas Reporter - December 2011 - 82
American Oil & Gas Reporter - December 2011 - R&D Areas Key to Improving Fracturing
American Oil & Gas Reporter - December 2011 - 84
American Oil & Gas Reporter - December 2011 - 85
American Oil & Gas Reporter - December 2011 - 86
American Oil & Gas Reporter - December 2011 - 87
American Oil & Gas Reporter - December 2011 - 88
American Oil & Gas Reporter - December 2011 - 89
American Oil & Gas Reporter - December 2011 - 90
American Oil & Gas Reporter - December 2011 - Natural Gas Offers Solutions as Transportation Fuel
American Oil & Gas Reporter - December 2011 - 92
American Oil & Gas Reporter - December 2011 - 93
American Oil & Gas Reporter - December 2011 - 94
American Oil & Gas Reporter - December 2011 - 95
American Oil & Gas Reporter - December 2011 - Completion Design, Frac Modeling Optimize Eagle Ford Wells
American Oil & Gas Reporter - December 2011 - 97
American Oil & Gas Reporter - December 2011 - 98
American Oil & Gas Reporter - December 2011 - 99
American Oil & Gas Reporter - December 2011 - 100
American Oil & Gas Reporter - December 2011 - 101
American Oil & Gas Reporter - December 2011 - 102
American Oil & Gas Reporter - December 2011 - 103
American Oil & Gas Reporter - December 2011 - 104
American Oil & Gas Reporter - December 2011 - 105
American Oil & Gas Reporter - December 2011 - 106
American Oil & Gas Reporter - December 2011 - 107
American Oil & Gas Reporter - December 2011 - 108
American Oil & Gas Reporter - December 2011 - 109
American Oil & Gas Reporter - December 2011 - 110
American Oil & Gas Reporter - December 2011 - Novel Drill-In Fluid Excels in Horizontal ERD Wells
American Oil & Gas Reporter - December 2011 - 112
American Oil & Gas Reporter - December 2011 - 113
American Oil & Gas Reporter - December 2011 - 114
American Oil & Gas Reporter - December 2011 - 115
American Oil & Gas Reporter - December 2011 - 116
American Oil & Gas Reporter - December 2011 - Technologies Optimize Sand Control
American Oil & Gas Reporter - December 2011 - 118
American Oil & Gas Reporter - December 2011 - 119
American Oil & Gas Reporter - December 2011 - 120
American Oil & Gas Reporter - December 2011 - 121
American Oil & Gas Reporter - December 2011 - Operators Must Manage Risk Before, During and After Drilling
American Oil & Gas Reporter - December 2011 - 123
American Oil & Gas Reporter - December 2011 - 124
American Oil & Gas Reporter - December 2011 - 125
American Oil & Gas Reporter - December 2011 - 126
American Oil & Gas Reporter - December 2011 - 127
American Oil & Gas Reporter - December 2011 - 128
American Oil & Gas Reporter - December 2011 - OCS Access: BOEM Offers Business-as-Usual OCS Leasing Plan
American Oil & Gas Reporter - December 2011 - Court Finds for Insurers in Gulf Spill Ruling
American Oil & Gas Reporter - December 2011 - 131
American Oil & Gas Reporter - December 2011 - 132
American Oil & Gas Reporter - December 2011 - OIPA
American Oil & Gas Reporter - December 2011 - 134
American Oil & Gas Reporter - December 2011 - 135
American Oil & Gas Reporter - December 2011 - Clean Air Act
American Oil & Gas Reporter - December 2011 - 137
American Oil & Gas Reporter - December 2011 - IOGA NY
American Oil & Gas Reporter - December 2011 - 139
American Oil & Gas Reporter - December 2011 - 140
American Oil & Gas Reporter - December 2011 - 141
American Oil & Gas Reporter - December 2011 - 142
American Oil & Gas Reporter - December 2011 - 143
American Oil & Gas Reporter - December 2011 - COGA
American Oil & Gas Reporter - December 2011 - 145
American Oil & Gas Reporter - December 2011 - 146
American Oil & Gas Reporter - December 2011 - IPAA Annual
American Oil & Gas Reporter - December 2011 - 148
American Oil & Gas Reporter - December 2011 - 149
American Oil & Gas Reporter - December 2011 - 150
American Oil & Gas Reporter - December 2011 - 151
American Oil & Gas Reporter - December 2011 - Louisiana
American Oil & Gas Reporter - December 2011 - 153
American Oil & Gas Reporter - December 2011 - 154
American Oil & Gas Reporter - December 2011 - 155
American Oil & Gas Reporter - December 2011 - West Virginia
American Oil & Gas Reporter - December 2011 - 157
American Oil & Gas Reporter - December 2011 - Pennsylvania
American Oil & Gas Reporter - December 2011 - Texas
American Oil & Gas Reporter - December 2011 - 160
American Oil & Gas Reporter - December 2011 - The American Well Servicing Directory, Winter 2011
American Oil & Gas Reporter - December 2011 - 162
American Oil & Gas Reporter - December 2011 - 163
American Oil & Gas Reporter - December 2011 - 164
American Oil & Gas Reporter - December 2011 - 165
American Oil & Gas Reporter - December 2011 - 166
American Oil & Gas Reporter - December 2011 - 167
American Oil & Gas Reporter - December 2011 - 168
American Oil & Gas Reporter - December 2011 - 169
American Oil & Gas Reporter - December 2011 - 170
American Oil & Gas Reporter - December 2011 - 171
American Oil & Gas Reporter - December 2011 - 172
American Oil & Gas Reporter - December 2011 - 173
American Oil & Gas Reporter - December 2011 - 174
American Oil & Gas Reporter - December 2011 - 175
American Oil & Gas Reporter - December 2011 - 176
American Oil & Gas Reporter - December 2011 - 177
American Oil & Gas Reporter - December 2011 - 178
American Oil & Gas Reporter - December 2011 - 179
American Oil & Gas Reporter - December 2011 - 180
American Oil & Gas Reporter - December 2011 - 181
American Oil & Gas Reporter - December 2011 - 182
American Oil & Gas Reporter - December 2011 - 183
American Oil & Gas Reporter - December 2011 - 184
American Oil & Gas Reporter - December 2011 - 185
American Oil & Gas Reporter - December 2011 - Industry Focus
American Oil & Gas Reporter - December 2011 - 187
American Oil & Gas Reporter - December 2011 - 188
American Oil & Gas Reporter - December 2011 - 189
American Oil & Gas Reporter - December 2011 - 190
American Oil & Gas Reporter - December 2011 - 191
American Oil & Gas Reporter - December 2011 - Classified Advertising
American Oil & Gas Reporter - December 2011 - 193
American Oil & Gas Reporter - December 2011 - Advertisers Index
American Oil & Gas Reporter - December 2011 - Cover3
American Oil & Gas Reporter - December 2011 - Cover4
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