Several processing methods in both time and frequency domains have been used to compute the in-situ specific dissipation function I/Q, or its inverse, the quality factor Q, in water-saturated unconsolidated sediments. These methods are based on measurements of spectral amplitude ratio, peak-to-peak and first-peak amplitude ratio, rise time, pulse broadening, and the Futterman causal attenuation operator of an attenuating signal.Compressional seismic waves were generated from explosive sources ranging in size from 1 to 64 mg of silver azide and recorded at a depth of 7.62 m below the surface near Wendover, Utah. The medium consisted of silty sandy clays with mean grain size diameter of 7.48 urn and water saturation of 70 percent. The hydrophone receivers were spirally distributed at distances ranging from 25 to 200 m from the source.An average Q value of 26 was obtained using analysis of spectral amplitude ratios over the frequency range 450--725 Hz for the five different sizes of explosive
Early stimulation work in Peat Field of Queensland, Australia involved application of cavity completion techniques to produce methane gas at commercial rates in the first wells completed in the reservoir gas cap. Early in the project life, cavity completion treatments resulted in promising and acceptable gas flow rates. However, excessive cost associated with this technique led to consideration of alternate stimulation approaches by the design team. The main objective was to achieve similar or better gas rates at the lowest cost. Multi-seam nitrogen-foam stimulation was conducted in several wells of the Peat field to assess the effectiveness of this technique in terms of:production enhancement and cost reduction;location of the coal-seam intervals in the gas cap (i..e. gas-saturated coals) and;improved completion efficiency. To minimise the effects of tortuosity and multiple far-field fractures in addition to ensuring that each coal-seam interval received adequate treatment, a staged stimulation approach in combination with other remedies such as sand slugs and high injection rates was adopted and successfully applied. Zonal Isolation was achieved through the use of the newly developed, easily drillable composite plugs that allow staged treatment with flowback capabilities. Field data of representative Peat wells will be used to demonstrate the successful application of the hydraulic fracturing approach that resulted in methane gas rates that more than compete with the early cavity completion techniques either from a cost or production improvement point of view. The following specifics are addressed in the paper:A novel fracture design approach and modeling of fracturing treatments that can be of value to a broad audience of operators and design engineers.Real-time fracture stimulation methodology, analysis, and execution.Remedies to minimize the near-wellbore tortuosity and multiple far field fractures to avoid premature "screenout" and carry the fracture treatment to completion.Chemical optimization of fracture fluid designed based on coal characteristics.Use of newly developed composite epoxy-glass fracture and bridge plugs that provide a more efficient and cost effective way to carry out staged stimulation treatments.Post-fracture production tests to estimate the nitrogen-foam fracture treatment effectiveness in multi-seam CBM wells. Introduction The Peat field1 is located on the eastern edge of the Bowen Basin about 20 km east of the town of Wandoan (Fig. 1). The field is approximately 8 km wide and 26 km long and comprises Late Permian Baralaba Coal Measures overlying the Burunga Anticline, the largest anticlinal feature in the Bowen Basin. Aggregate net coal thicknesses range from about 7.1 m to 22.7 m over an interval of between 100 m to 140 m. Individual seam thicknesses range up to 13.7 m. Coal depths range from 600 m below ground and are currently being investigated to as deep as 1200 m. Within 15 km to the west coal depths reach over 2000 m.
Compressional velocity and attenuation were measured as a function of depth in layer 3 gabbros from the recovered core at Ocean Drilling Program Site 735. High-frequency (400 kHz) acoustic transmission experiments were conducted on 117 minicore samples under room conditions of temperature and pressure on board the JOIDES Resolution. Although experimental errors were large in some deformed samples, the average of our measurements of 1000/(λ, on these samples is 49 ± 32. Ultrasonic tests on a \% porosity sample at elevated effective pressures from 10 up to 500 MPa showed an increase in V_ from 6.8 to 7.0 km/s and a decrease in \000/Q p from 26 to 23. The small pressure dependence of attenuation in these low-porosity gabbros enables one to use measurements at room conditions for relative interpretation as a function of depth.These measurements of 1000/(λ, vs. depth show (1) an overall decrease in attenuation from lithologic Units II through V as a function of depth, (2) a 10-fold decrease in the average variance in the measurement in lithologic Unit II, and (3) an inverse relationship between average velocity and average attenuation. An explanation for these results is that tectonized rock fabrics have a significant effect on the measurement of attenuation and velocity. The future use of this simple shipboard operation to measure trends in attenuation as a function of depth may be effective to determine the degree of alteration and tectonism in similar, nonpressure-sensitive rocks.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.