Best Practices

Differences With Stimulation Models

Table 1 suggests some of the differences between hydraulic fracturing for stimulation and hydraulic fracturing during water injection. Settari and Warren, 1994, described modeling of waterflood-induced fractures and the features that distinguish this process from conventional hydraulic fracturing. First, there are basic philosophical differences. In produced water reinjection or waterflooding, injectivity can be maintained if fracturing occurs. However, the engineer must consider more than the immediate impact of stimulation. Production economics are an essential consideration. A fracture alters the displacement pattern and can potentially decrease (or increase) recovery. There are significant differences in the time scale of the operations and the injected fluid viscosity. In water injection, the efficiency can be close to zero. "As a result, waterflood fracturing is leak-off dominated as opposed to stimulation fracturing which is leak-off controlled." Settari and Warren suggested that the following factors might be important for produced water reinjection or waterflooding situations.

Significant pressure and saturation gradients may exist around the well from previous field injection or production. Reservoir properties may not be constant.
There can be large-scale reservoir heterogeneity and consequently leakoff variation.
Other offset producers or injectors will affect fracture propagation.
There can be thermally altered stresses, and changes in the fluid properties.
The average reservoir pressure can change during the time-scale of the injection operations.

Some of the relevant differences are described on the following pages. It is essential to recognize that an important difference between hydraulic fracturing for stimulation and hydraulic fracturing during waterflooding is that, during stimulation activities, the fracture will propagate (much) faster than the leakoff fluid front.

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Introduction Click here to return to an introductory discussion of the concepts required for PWRI fracture modeling. If you want to go back to a different page, select the link from the table below.

An Introduction to PWRI Models

Mechanical Properties>

Mechanical Properties Are mechanical properties, such as Young's Modulus and Poisson's ratio, important in PWRI fracture modeling? If you want to skip forward, you can select from links in the table below.

Differences From Stimulation Models

Types of PWRI Models

Audit of PWRI Models

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