Unconventional/complex reservoirs

Extended Laterals and Hydraulic Fracturing Redevelop Tight Fractured Carbonates

The authors investigate the utility of applying unconventional technology to low- or variably producing carbonate reservoirs to increase estimated ultimate recovery and decrease development-scale variability.

Idealized diagram of Eagle Ford and Austin Chalk well spacing. Blue represents Eagle Ford and red Austin Chalk. Eagle Ford lateral well spacing is 450 ft, and Austin Chalk is 900 ft. The hypotenuse distance from Eagle Ford to Austin Chalk is 270 ft.
Fig. 1—Idealized diagram of Eagle Ford and Austin Chalk well spacing. Blue represents Eagle Ford and red Austin Chalk. Eagle Ford lateral well spacing is 450 ft, and Austin Chalk is 900 ft. The hypotenuse distance from Eagle Ford to Austin Chalk is 270 ft.
Source: SPE 216292.

In the complete paper, the authors compare development scenarios in a fractured carbonate play between historic vertical and short horizontal development and modern hydraulically fractured extended lateral development. Because of its long production history and recent redevelopment efforts, the Austin Chalk was chosen as a natural laboratory to test how recent artificial stimulation techniques can lead to additional production from a wider range of pore systems.

Development of the Austin Chalk

In recent years, application of modern unconventional multistage hydraulic fracturing techniques, coupled with adding proppant to support induced fracture networks, mitigated the steep decline seen in historic production profiles. These improvements were exemplified in a recent Austin Chalk redevelopment where modern completions led to an increase in estimated ultimate recovery (EUR) by 250% on average.

In the targeted area of development, historic, short Austin Chalk laterals without modern completions exhibited a wide range of well performance. Some outlier wells achieved high recoveries from accessing an existing natural fracture network with the original completion, whereas others, after only a few months of economic production, were unable to achieve continuous flow without a propped stimulation.

The differences in performance partially can be explained by the fact that the reservoir quality of different intervals within the Austin Chalk is likely highly variable.

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