Properties Of Strata Research Articles

2-D finite element modeling for seismic wave response in media with sand bodies

Forward modeling plays an important role in structural trap exploration because of its usefulness in identifying seismic wave characteristics. Structural traps have been discovered in the Dongpu depression of Zhongyuan Oil Field of China. However, its proved reserves still fall far short of total estimated reserves, suggesting that there are undiscovered lithologic traps. According to the stratum properties revealed by borehole surveying and exploration seismograms, we have constructed the models of deposit sand body traps and conducted a complex seismic wave modeling study using the finite element method. Our models contain scattering bodies. The trap media is considered viscous–elastic and finite element equations are derived with artificial boundary terms. The absorbing effect of the artificial boundary terms we obtained is fairly good. The source is simulated by concentrated forces or explosive sources. We obtain the common source/receiver record profiles by putting secondary sources directly on the interface nodes. Direct waves and surface waves of single-shot seismograms can be removed with Huygen's principle. We also put the filter of instrument response into the theoretical seismograms. In the paper, we have designed several models of sand bodies, and obtained their realistic seismic profiles with the finite element method. The corresponding records have been analyzed and the characteristics have been extracted. The method will provide an analytical tool for exploring lithologic traps effectively.

Tectonic structures, strata properties and rockbursts occurrence in a French coal mine : Gaviglio, P; Revalor, R; Piguet, J P; Dejean, M Proc 2nd International Symposium on Rockbursts and Seismicity in Mines, Minneapolis, 8–10 June 1988P289–293. Publ Rotterdam: A A Balkema, 1990

Tectonic structures, strata properties and rockbursts occurrence in a French coal mine : Gaviglio, P; Revalor, R; Piguet, J P; Dejean, M Proc 2nd International Symposium on Rockbursts and Seismicity in Mines, Minneapolis, 8–10 June 1988P289–293. Publ Rotterdam: A A Balkema, 1990

Assessment of blasting efficiency by seismic surveys and rope shovel performance monitoring: A case study

ABSTRACT In this paper, diggability assessment studies for an electrical rope shovel undertaken in a producing surface lignite mine is presented. For this purpose, a test bench is selected and shovel performance monitoring together with various surveys were carried out on this bench. Manual stopwatch surveys, recording of peak and mean power consumption of the shovel were made before and after blasting. Mass and material properties of the overburden strata were defined, seismic surveys were conducted to measure in-situ P-wave velocities before and after blasting. Bock Quality Indexes were established during blasthole drilling in order to correlated with any local variation in the overburden strata. The accumulated data was analysed in order to examine the efficiency of blasting and its likely effect on the rope shovel performance in terms of production capacity and power consumption. Furthermore a cost analysis is made in order to demonstrate the differentiation of unit handling costs between direct diggi...

Tectonic structures, strata properties and rockbursts occurrence in a French coal mine : Gaviglio, P; Revalor, R; Piguet, J P; Dejean, M Proc 2nd International Symposium of Rockbursts and Seismicity in Mines, Minneapolis, 8–10 June 1988P409–426. Publ Minneapolis: University of Minnesota, 1988

Tectonic structures, strata properties and rockbursts occurrence in a French coal mine : Gaviglio, P; Revalor, R; Piguet, J P; Dejean, M Proc 2nd International Symposium of Rockbursts and Seismicity in Mines, Minneapolis, 8–10 June 1988P409–426. Publ Minneapolis: University of Minnesota, 1988

The role of low-permeability rocks in regional flow

Summary The role of low-permeability rocks in determining fluid migration within sedimentary basins has been shown to be crucial for deriving the direction and rate of fluid movement. The magnitude of the flows depends on the geometry of the sedimentary basin and on the bulk hydrogeological properties of the various strata and their relative values. Measurements of head and pore-water compositions of argillaceous formations show separate evidence for the existence of cross-formational flow resulting in groundwaters of mixed origins. Numerical and analytical models have been developed and applied to some basinal systems in England. They have been used to assess the directions of groundwater flow likely to be encountered by repository site investigation programmes and to aid in the interpretation of groundwater head and chemistry data. Such flow models still require detailed validation. Our knowledge of the flow mechanism and the physical properties of mudrocks at depth is still elementary, but the indications are that the role of low-permeability rocks in controlling fluid migration has been much underestimated.

Method for determining the degree of change of material properties of underground strata

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Experimental concretes for sealing radioactive-waste repositories in evaporite strata

Rock fractions form a sequence of evaporite strata have been used as aggregate in cement-based composites, prepared to simulate materials for sealing a geologic repository for radioactive waste. Five types of coarse aggregate simulated mined-out backfill for normally mixed or preplaced-aggregate concrete. Geochemical properties of evaporite strata were considered in choosing the brine, rocks, and cement formulation for these experiments. Adequate values (>35 MPa) were obtained for compressive strengths of concrete cast with dolostone and anhydrite aggregate; these samples also had very low permeabilities to brine, 10 −7 or 10 −8 μm 2 (darcy). Tests of samples with halite aggregate are promising. A strong bond apparently was formed between the grout and the various rocks, evidenced by breakage0 through aggregate particles in tests of compressive strength. From these experiments, acceptability criteria have been developed for simulated shaft-sealing composites.

Predicting the Performance of Injection Operations In Stratified or Pseudo-Stratified Formations

Abstract Nearly all petroleum reservoirs are either truly separated into strata of different flow properties, or have heterogeneities which can be treated as such stratification. In pattern injection operations this can lead to a quite different production history than would be computed for a homogeneous reservoir. The usual way to consider such stratification has been typified by the Stiles or Dykstra-Parsons approaches which consider all well injection patterns to result in linear flow. This paper details a general method for using either computed or measured (on scale models) individual stratum production histories and conductivity ratios to obtain a combined production history for the stratified systems mentioned above. The method considers the proper well geometry and the flow and saturation characteristics of the individual strata. Introduction Almost without exception, petroleum reservoirs are non-homogeneous in rock characteristics such as permeability and porosity. Most of our oil recovery predictions are based on the concept of homogeneous rocks. We must therefore try to adjust or adapt these if we wish to obtain realistic recovery predictions. One of the most common types of reservoir heterogeneity is permeability and porosity stratification. This is typified by a reservoir consisting of two or more blanket-like oil bearing strata which can be traced from well to well in the field. Each of these strata can often be considered homogeneous in permeability and porosity. The strata can be separated by impermeable layers (such as shale). In this case they will act as separate reservoirs with common boundary conditions. The strata can also be contiguous so that fluids may flow freely from one to the other at any point of contact. In this case, the flow of fluids is more difficult to predict. Another common type of reservoir heterogeneity is a variation in rock properties that do not occur in any regular manner. Recovery predictions are usually made by equating this complex system to a system of discrete strata of individually uniform properties. Several statistically- based methods for converting core sample properties into a pseudo-stratified reservoir are in common usage. These end by plotting permeabilities (in ascending order) vs reservoir height, and then dividing this into the most plausible system of individual strata. To be most effective, these pseudo-strata should not only have individual permeabilities but also appropriate values for porosity, initial oil in place, recoverable oil, relative permeabilities, etc. Once resolved in pseudo-strata, this type of reservoir can be treated in the same way as the real stratified systems except that there is no possibility of impermeable layers between the pseudo-strata. Published Methods for Stratified Reservoirs Computational methods for predicting secondary recovery results in stratified systems generally assume that fluids cannot flow from one stratum into another even though crossflow between the strata is possible. This assumption is probably reasonable as long as the mobility ratio is unfavorable (M >1).* Few secondary recovery operations have favorable mobility ratios except for the oil bank fill-up period. One of the first methods to be published and widely used was that of Stiles. This method assumed that the reservoir was made up of linear strata of different permeabilities and that the mobility ratio between the injected fluid and the produced fluid was 1. All other properties of the strata were considered equal, Dykstra and Parsons enlarged this method to include the effects of unequal fluid mobilities.',' However, the assumptions of a linear flow system and identical stratum properties (except specific permeability) were kept. Neither method treated the case of a waterflood in a reservoir containing a flowable gas phase. The Dykstra-Parsons method did introduce the concept of changing fluid velocity in each stratum as the injection continued. Two more recent publications use a stratum combination method that can be applied whenever volumetric sweep and fluid conductivity data for the appropriate homogeneous system are either available or can be computed. This method and some of its logical extensions will be further discussed. JPT

WELL LOGGING BY RADIOACTIVITY

A discussion of the relation of radioactivity curves to physical properties of strata studied, including the influence of the history of the rocks involved. Comparisons are made between the probable areal extent of correlatable horizons in various types of formations, and the ability of various logging methods to distinguish these layers is considered as an index of the geological usefulness of the various logging methods. The possibility of distinguishing altered zones which do not show marked physical differences fom the neighboring rocks (such as faults and unconformities), is discussed, and its bearing on the usefulness of radioactivity logging is considered. Illustrations of the correlating power of radioactivity logs are given. Comparisons with electrical logs and with geological sample logs are shown to illustrate the points discussed. A brief discussion of the development of the radioactivity logging method and of the technique of carrying out field operations is also given.

VII.—The Water-Bearing Strata in the Neighbourhood of Norwich

The Extensive Excavations For Sewerage purposes, which have been X going on for nearly two years, have brought to light several peculiarities in the relative water-bearing properties of the various strata in the neighbourhood of Norwich.