Distinguished Author Series articles are general, descriptive representations that summarize the state of the art in an area of technology by describing recent developments for readers who are not specialists in the topics discussed. Written by individuals recognized as experts in the area, these articles provide key references to more definitive work and present specific details only to illustrate the technology. Purpose: to inform the general readership of recent advances in various areas of petroleum engineering.
To obtain optimal results from the fracturing process, several new fracturing technologies can be applied to prevent inappropriate stimulation designs and catastrophic fracture-fluid problems. Despite industry awareness of these technologies, they are not applied routinely because of their added expense. In addition, the benefits are difficult to quantify and often are not clearly understood. In this paper, we present an economic assessment of fracture-treatment quality control, in-situ stress profiling, and 3Dfracture-propagation models that indicates that these technologies increase gas reserves by 10% to 20% for a 5% to 10% increase in the well cost. The application of these technologies is profitable when the formation gas permeability is between 0.001 and 0.3 md.
In recent years, hydraulic fracturing research performed by the Gas Research Inst. (GRI) and other industry organizations has generated a wealth of new technology, including the GRI Mobile Testing and Control Facility, the GRI Rheology Unit, FRACPRO (a 3D fracture design program), the Treatment Analysis Unit, procedures for developing in-situ stress profiles, and microseismic processing techniques to determine fracture height and azimuth. Also, field experiments performed on Cooperative Research and Staged Field Experiment (SFE) wells have provided comprehensive data sets for developing and testing new ideas.
Our field research shows that the in-situ stress contrasts between rock layers and fracture-fluid viscosity are often quite different from the values assumed or estimated by the design engineer. Errors in assumed values of the in-situ stress contrast lead to inaccurate reservoir descriptions and inappropriate stimulation designs. Fracture-fluid problems compound the situation through poor proppant transport or fracture plugging with unbrokengel.