Fracture Orientation Analysis by the Solid Earth Tidal Strain Method (1982)

Fracture Orientation Analysis by the Solid Earth Tidal Strain Method Jonathan M. Hanson; Jonathan M. Hanson Terra Tek Research Search for other works by this author on: This Site Google Scholar Lawrence B. Owen Lawrence B. Owen Terra Tek Research Search for other works by this author on: This Site Google Scholar Paper presented at the SPE Annual Technical Conference and Exhibition, New Orleans, Louisiana, September 1982. Paper Number: SPE-11070-MS https://doi.org/10.2118/11070-MS Published: September 26 1982 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Hanson, Jonathan M., and Lawrence B. Owen. "Fracture Orientation Analysis by the Solid Earth Tidal Strain Method." Paper presented at the SPE Annual Technical Conference and Exhibition, New Orleans, Louisiana, September 1982. doi: https://doi.org/10.2118/11070-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search Dropdown Menu nav search search input Search input auto suggest search filter All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE Annual Technical Conference and Exhibition Search Advanced Search AbstractA new practical method has been developed to estimate subsurface fracture orientation based on art analysis of solid earth tidal strains. The tidal strain fracture orientation technique is a passive method which has no depth limitation. The orientation of either natural or hydraulically stimulated fractures can be measured using either new or "old" static observation wells. Estimates for total compressibility and areal interconnected porosity can also be developed for reservoirs with matrix permeability using a combination of tidal and barometric strain analysis. Data acquisition requirements are modest and no surface instrumentation beyond pressure monitoring equipment is required. The tidal method has been successfully demonstrated at a naturally fractured geothermal field (Raft River) in South eastern Idaho and at an oil field in Western Canada. Both case studies are described.IntroductionObservations of fluid pressure response in wells due to solid earth tides have been made in a variety of geologic and hydrologic environments. Two of the first observations were made at a flooded coal mine in Europe in 1879 and later in wells in South Africa from 1905 to 1912. More recent observations have been reported in ground-water aquifers; in naturally fractured crystal-line rock; in fractured and unfractured oil and gas reservoirs; and in geothermal reservoirs. With few exceptions, interpretations of fluid pressure response to solid earth tides have been made based on a model of a homogeneous isotropic confined or unconfined aquifer intersected by a well. The fluid is assumed to be single phase and the flow model, where one is used, is one-dimensional. Wellbore storage effects have often been ignored in these interpretations. These models indicate that well pressure response to solid earth tidal strain depends primarily on the formation specific storage coefficient and matrix primarily on the formation specific storage coefficient and matrix permeability. Furthermore, as Bredehoeft has pointed out, it may be permeability. Furthermore, as Bredehoeft has pointed out, it may be possible to evaluate connected porosity by using Jacob's relationship possible to evaluate connected porosity by using Jacob's relationship between barometric efficiency and specific storage. Barometric efficiency is defined as the proportionality constant relating the change in aquifer fluid pressure to the change in atmospheric pressure load on the Earth's surface. Prior attempts to apply the tidal response approach to reservoir data for the determination of specific storage and/or porosity have met with limited success due primarily to limitations in existing tidal strain models and inappropriate spectral analysis techniques. In this paper we describe methods for determining fracture orientation, specific storage and porosity. porosity.FRACTURE ORIENTATIONTidal strain is a tensor quantity. Thus, there are certain well-defined directional characteristics associated with the applied crustal deformation due to tidal effects. Measured fluid pressure response to solid earth tides is intimately linked to formation deformation. Hanson first noted that measured fluid pressure fluctuations contain information regarding the nature of formation deformation including fracture orientation and reservoir structure. Subsequently, others have interpreted water level changes in a crystalline formation intersected by a few discrete fractures in terms of fracture geometry.Use of a tidal response method as a practical reservoir assessmeit tool requires the ability to resolve pressure signals on the order of 10 to 10, psi. In some cases, tidal response may be masked by background noise in the pressure signal. The availability of high resolution quartz pressure transducers make it possible to directly resolve pressure pressure transducers make it possible to directly resolve pressure perturbations of 0.01 psi. Since tidal signals are the sum of sinusoidal perturbations of 0.01 psi. Since tidal signals are the sum of sinusoidal components that are repetitive in nature, information-theoretic methods can be used to improve resolution. Given sufficient data, tidal information can always be resolved regardless of the signal-to-noise ratio. Keywords: response method, fracture, porosity, frequency, geothermal reservoir, fluid dynamics, equation, tidal potential, drillstem testing, pressure response Subjects: Hydraulic Fracturing, Reservoir Characterization, Reservoir Fluid Dynamics, Formation Evaluation & Management, Non-Traditional Resources, Flow in porous media, Drillstem/well testing, Geothermal resources This content is only available via PDF. 1982. Society of Petroleum Engineers You can access this article if you purchase or spend a download.