Example 1
High-Resolution Imaging Using Microseismic Events on DAS Data.
Using the high-frequency data recorded in DAS array to form high-resolution seismic images, which are used to image hydraulic fractures. The embodiment of this example has several advantages or prior systems, including: (a) Sensors are closer to the sources thus can provide much higher frequency comparing to traditional surface seismic data; (b) microseismic data generally carries frequency around 200 Hz while the surface seismic data is usually below 30 Hz. High-frequency data will improve the spatial-resolution of seismic images; (c) microseismic data have much stronger S-wave amplitude comparing to the surface seismic data, which is dominated by P-wave. S-wave is sensitive to the highly compliant fluids. Thus, the seismic attributes derived from the S-wave seismic images can be used to identify the fluid-filled hydraulic fractures; (d) DAS array forms much larger aperture (generally much greater than 2000 feet) comparing to traditional geophones (usually less than 2000 feet), while having much smaller spatial interval between the sensors. Those properties are ideal for producing high-resolution seismic images.
A velocity model is built using known-sources, such as (perforation shots) and microseismic events. Next microseismic events using geophone or DAS arrays are located. From this a reflection traveltime table between sources/sensors to the image voxels is computed. Next events on the DAS data are identified, provided they are located by geophones. The DAS data is then migrated to form a seismic image. Computations are then performed on the seismic attributes for fracture identification.
It is noted that there is no requirement to provide or address the theory underlying the novel and groundbreaking production rates, performance or other beneficial features and properties that are the subject of, or associated with, embodiments of the present inventions. Nevertheless, various theories are provided in this specification to further advance the art in this important area, and in particular in the important area of hydrocarbon exploration and production. These theories put forth in this specification, and unless expressly stated otherwise, in no way limit, restrict or narrow the scope of protection to be afforded the claimed inventions. These theories many not be required or practiced to utilize the present inventions. It is further understood that the present inventions may lead to new, and heretofore unknown theories to explain the conductivities, fractures, drainages, resource production, and function-features of embodiments of the methods, articles, materials, devices and system of the present inventions; and such later developed theories shall not limit the scope of protection afforded the present inventions.
The various embodiments of restimulation operations set forth in this specification may be used for various oil field operations, other mineral and resource recovery fields, as well as other activities and in other fields. Additionally, these embodiments, for example, may be used with: oil field systems, operations or activities that may be developed in the future; and with existing oil field systems, operations or activities which may be modified, in-part, based on the teachings of this specification. Further, the various embodiments set forth in this specification may be used with each other in different and various combinations. Thus, for example, the configurations provided in the various embodiments of this specification may be used with each other; and the scope of protection afforded the present inventions should not be limited to a particular embodiment, configuration or arrangement that is set forth in a particular embodiment, example, or in an embodiment in a particular Figure.
The invention may be embodied in other forms than those specifically disclosed herein without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive.
