Carthage Cotton Valley Fracture Imaging Project - Imaging Methodology and Implications

Abstract

SPE Paper 38577 introduced the Carthage Cotton Valley Hydraulic Fracture Imaging Project and described the initial imaging work. This paper describes the most recent methodology and implications of imaging hydraulic fractures utilizing microseisms recorded by extensive sensor arrays. Initial imaging work utilized a forward modeling approach. This paper will report further on confirmation of the event locations by inversion methods and by using decimation studies. A source parameter analysis will also be presented. Cotton Valley fracture treatments were performed at depths near 10,000 ft and imaged with arrays cemented in offset wells approximately 1300' away. Several techniques are utilized in both event location analysis and in analyzing certain characteristics of the events. These methodologies provide interpretations of the actual fractures and therefore have implications in the design and modeling of fractures. This paper will also point out and verify the need for development of an economical and commercial service to image fractures in real time. Decimation studies utilizing fewer optimally spaced receptors will determine the ability to develop a commercial service. Imaging of the hydraulic fractures at the Cotton Valley test site provides conclusions not easily accepted. Issues such as asymmetry, dimensions of the fracture and growth characteristics all prove to be substantially different than expected. Findings such as these will affect modeling techniques, design parameters, and eventually well spacing and development plans. Accurate mapping of a fracture will provide conclusive information that can be utilized to develop optimized and efficient fracture treatments. More effective fracture treatments will result in reduced well costs which allow field extension and expansion opportunities. Any operator or service company should apply lessons learned and presented in this paper. Imaging of the fracture and analysis of the actual failure mechanisms will provide a basis from which to design and model fractures in the Cotton Valley formation. Ideas for technology and completion strategies could be applicable to tight gas sand completions in other areas. This paper will show technical contributions such as:State of the art technologies utilized for mapping of the fractures.Analysis techniques that will be paramount in the future development of a commercial fracture mapping technology.Event parameter analysis yielding deductions concerning actual failure types in the rock. These analyses will have a major impact on fracture design and modeling. P. 599

An Evaluation of Microseismic Monitoring of Lenticular Tight Sandstone Stimulations

“…Comprehensive microseismic testing was also performed at the Cotton Valley Hydraulic Fracture Imaging Project (Walker et al 1998;Mayerhofer et al 2000;Rutledge et al 2004), but there were no ground truth measurements to confirm the microseismic results. Similarly, comprehensive testing was performed at the Mounds Drill Cuttings Injection Field Experiment (Peterson et al 2001), but the microseismicity was very limited as a result of small volumes and low injectate rates, thus making any validation assessment somewhat limited.…”

Source-Mechanism Studies on Microseismicity Induced by Hydraulic Fracturing

“…Microseismic mapping is a technology that has proven valuable for monitoring stimulations in unconventional reservoirs, such as gas shales and tight-gas sandstones (Hart et al 1984;Warpinski et al 1990;Walker et al 1998;Fisher et al 2002;Maxwell et al 2002;Griffin et al 2003;Fisher et al 2004;Warpinski et al 2005;Cipolla et al 2005;Mayerhofer et al 2005;Wolhart et al 2005;Wolhart et al 2006;Shemeta et al 2007;Vulgamore et al 2007;Daniels et al 2007;King et al 2008;Potapenko et al 2009;Waters et al 2009). It is performed by fielding a large array(s) of highly sensitive and high-frequency-response three-component geophones or accelerometers in an offset well(s) in close proximity to an interval that is being stimulated.…”