Pressure diffusion waves in porous media

Summary Pressure diffusion wave in porous rocks are under consideration. The pressure diffusion mechanism can provide an explanation of the high attenuation of lowfrequency signals in fluid-saturated rocks. Both single and dual porosity models are considered. In either case, the attenuation coefficient is a function of the frequency

An object-oriented cluster search algorithm

In this work we describe two object-oriented cluster search algorithms, which can be applied to a network of an arbitrary structure. First algorithm calculates all connected clusters, whereas the second one finds a path with the minimal number of connections. We estimate the complexity of the algorithm and infer that the number of operations has linear growth with respect to the size of the network

Using frequency-dependent siesmic attributes in imaging of a fractured reservoir zone

Normal reflection from a fractured reservoir is analyzed using frequency-dependent seismic attributes. Processing of 3D low-frequency seismic data from a West-Siberian reservoir produced an accurate delineation of the fracturedhydrocarbon-bearing zones. P-wave propagation, reflection and transmission at an impermeable interface between elastic and dual-porosity poroelastic media is investigated. It is obtained that the reflection and transmission coefficients are functions of the frequency. At low frequencies, their frequency-dependent components are asymptotically proportional to the square root of the product of frequency reservoir fluid mobility and fluid density

Pressure diffusion waves in porous media

Pressure diffusion wave in porous rocks are under consideration. The pressure diffusion mechanism can provide an explanation of the high attenuation of low-frequency signals in fluid-saturated rocks. Both single and dual porosity models are considered. In either case, the attenuation coefficient is a function of the frequency

Replacing annual shut-in well tests by analysis of regular injection data: Field-case feasability study

Regulations governing deep injection of industrial wastes for disposal require regular tests for monitoring the formation hydraulic properties changes in the vicinity of the wellbore. Such a monitoring is performed through transient pressure well testing, a procedure that is routinely used in the environmental and oil industries. In such tests, the pumping pressures and rates are recorded and analyzed to estimate the transmissivity and storativity of the rock in the vicinity of the wellbore. Numerous methods for analyzing such data have been developed since the pioneering paper by Theis (1935). The well test analysis methods are summarized in several monographs, see, e.g., Earlougher (1977) and Matthews (1967). Traditional well test analysis methods are often based on estimating the slope of the pressure fall-off curve in a special time scale, e.g., using the Horner plot method (Horner, 1951). Such an approach is justified by asymptotic analysis of the pressure change relative to a uniform initial pressure distribution. However, in reality, such an initial condition may not hold true because the operations preceding the test make the pressure distribution not uniform. It has been demonstrated in Silin and Tsang (2002, 2003) that in the Horner plot method, this circumstance partially explains the deviation of the data points from the theoretically predicted straight line. A new method has been proposed to analyze well test data accounting for the pre-test operations. This method has been validated using synthetic and field well test data. In this paper, we demonstrate how the method can be applied to analyze regular pumping data from an injection field to estimate the formation's hydraulic properties without interrupting the operations. In this estimation, we use the code ODA developed at Berkeley Lab. This code implements the methods and algorithms developed by Silin and Tsang (2002, 2003)

Replacing annual shut-in well tests by analysis of regular injection data: Field-case feasibility study

Regulations governing deep injection of industrial wastes for disposal require regular tests for monitoring the formation hydraulic properties changes in the vicinity of the wellbore. Such a monitoring is performed through transient pressure well testing, a procedure that is routinely used in the environmental and oil industries. In such tests, the pumping pressures and rates are recorded and analyzed to estimate the transmissivity and storativity of the rock in the vicinity of the wellbore. Numerous methods for analyzing such data have been developed since the pioneering paper by Theis (1935). The well test analysis methods are summarized in several monographs, see, e.g., Earlougher (1977) and Matthews (1967). Traditional well test analysis methods are often based on estimating the slope of the pressure fall-off curve in a special time scale, e.g., using the Horner plot method (Horner, 1951). Such an approach is justified by asymptotic analysis of the pressure change relative to a uniform initial pressure distribution. However, in reality, such an initial condition may not hold true because the operations preceding the test make the pressure distribution not uniform. It has been demonstrated in Silin and Tsang (2002, 2003) that in the Horner plot method, this circumstance partially explains the deviation of the data points from the theoretically predicted straight line. A new method has been proposed to analyze well test data accounting for the pre-test operations. This method has been validated using synthetic and field well test data. In this paper, we demonstrate how the method can be applied to analyze regular pumping data from an injection field to estimate the formation's hydraulic properties without interrupting the operations. In this estimation, we use the code ODA developed at Berkeley Lab. This code implements the methods and algorithms developed by Silin and Tsang (2002, 2003)

Reconstruction of Sedimentary Rock Based on Mechanical Properties

We describe a general, physics-based approach to numerical reconstruction of the geometrical structure and mechanical properties of natural sedimentary rock in 3D. Our procedure consists of three main steps: sedimentation, compaction, and diagenesis, followed by the verification of rock mechanical properties. The dynamic geologic processes of grain sedimentation and compaction are simulated by solving a dimensionless form of Newton's equations of motion for an ensemble of grains. The diagenetic rock transformation is modeled using a cementation algorithm, which accounts for the effect of rock grain size on the relative rate of cement overgrowth. Our emphasis is on unconsolidated sand and sandstone. The main input parameters are the grain size distribution, the final rock porosity, the type and amount of cement and clay minerals, and grain mechanical properties: the inter-grain friction coefficient, the cement strength, and the grain stiffness moduli. We use a simulated 2D Fontainebleau sandstone to obtain the grain mechanical properties. This Fontainebleau sandstone is also used to study the initiation, growth, and coalescence of micro-cracks under increasing vertical stress. The box fractal dimension of the micro-crack distribution, and its variation with the applied stress are estimated