Pore Fluid Content Research Articles

Pore Fluid Content and Void Ratio For Marine Sediments

ABSTRACT The pore fluid of marine sediments contains various salts that are in solution in water. Frequently, however, the existence of salts is not considered when utilizing the concepts of water content and void ratio. In this note, expressions for the contents of water and pore fluid and the void ratio for saturated marine sediments are derived in terms of the ‘water content’ in which the salinity is not taken into account. The water and pore fluid contents and void ratio calculated with ordinary values of the ‘water content’ and the salinity are presented. It is demonstrated that the water content, pore fluid content and the void ratio would be underestimated by the order of 5% unless the salinity is taken into account.

Seismic Response for Reservoir-Fluid Evaluation

Summary This paper describes a study of the relationships among lithology, pore-fluid content, stratigraphy, and the seismic response for clastic sedimentary rocks. We show how it is possible to generate seismic models from the petrophysical measurements. This procedure should provide a useful conceptual model for understanding the seismic response of a particular type of reservoir.

APPLICATION OF PETROPHYSICAL MEASUREMENTS TO THE PREDICTION OF SEISMIC RESPONSES OF DIFFERING LITHOLOGYOR PORE FLUIDS1

ABSTRACTDetermination of petrography and pore fluid content is an ultimate goal of an integrated seismic‐petrophysical study. For lack of a general inversion technique, forward modelling is useful in studying the relations between lithology, stratigraphy, pore fluid content and the seismic response. This report describes a study of two clastic sequences in Utah, from which 32 rock samples were analysed. A detailed petrographic study was done. Laboratory measurements were made of ultrasonic compressional‐ and shear‐wave velocity as a function of pressure. We computed the velocities at seismic frequencies for the samples when dry, over‐pressured, brine saturated, and oil saturated. The velocities were sensitive to the porosity, carbonate cementation and the depositional facies. We generated velocity profiles for hypothetical reservoirs for a range of saturation states. The velocity profiles were used to generate synthetic seismic shot gathers to study the seismic response of these clastic reservoirs. The fluid‐saturation strongly affects the seismic respone, as does the presence of a coal seam. An amplitude change with offset is often observed. However, stratigraphy appears to have a stronger effect on the seismic response.

A dielectric anomaly in electrolyte-saturated porous alumina ceramics

In order to understand the relation between the conductivity and the dielectric properties of porous materials and their pore fluid content, we report and discuss dielectric constant measurements of brine-saturated porous alumina ceramics which exhibit a gigantic increase of the low frequency dielectric constantwhile the sample remains conducting. Generalizing a model derived to study the properties of porous sedimentary rocks, where such an effect has been known for more than two decades, we discuss the effect of the pore geometry on the frequency, salinity and porosity variation of the ceramic dielectric constant and conductivity. This can provide a partial explanation of the reported measurements. Such a study provides a new and interesting method to investigate the microgeometry of composite materials and in particular the pore geometry of ceramics.

Geochemistry of a Marine Gas Hydrate Associated with a Bottom Simulating Reflector: ABSTRACT

End_Page 894------------------------------Multiple deployments of a pressurized core barrel (PCB) during drilling of DSDP-IPOD Site 533A on the Blake-Bahama Outer Ridge has provided conclusive evidence for the presence of gas hydrate in sediments exhibiting a well-defined bottom simulating reflector. Pressure decline curves monitored during degassing and sampling of two pressurized sediments clearly indicate a pressure plateau at about 1,500 kPa resulting from gas hydrate decomposition. The pressure decline curve also includes a region attributable to hydrostatic pressure and a sediment degassing region. The molecular compositions of volatile hydrocarbons in PCB gas samples were characterized by (a) less than 2% variation in the C1/C2 ratio during pressure release, (b) a fourfold increase in C36 hydrocarbons over the duration of the experiment, and (c) a tenfold increase in CO2 content of the expelled gases. Gas hydrate solids were recovered from Core 13-1 (~ 238 m depth) in sufficient quantity to permit several pressure/volume measurements. Gas expansion of the solids was measured at 13:1. Mole ratio of water to gas was found to be 50:1 after correcting for pore fluid content. Sediments remaining after gas hydrate decomposition were 93% H2O by weight. Most of the water contained in the sediments appeared to be associated with the gas hydrate. The hydrates recovered were extremely fine grained and decomposed rapidly upon removal from in-situ pressures and temperatures. End_of_Article - Last_Page 895------------

Experimentally produced preferred orientation in synthetic mica aggregates

An experimental study of the behaviour of micaceous aggregates undergoing deformation during and after mica growth has been undertaken using pelletised powder consisting of an oxide mix with the stoichiometry of phlogopite. The influences of temperature, pore fluid content, strain, strainrate, and pre-mixing time have been examined. It is concluded that oriented growth of anisotropic crystals, due either to anisotropy of pore structure and hence permeability or to pressure solution phenomena, gives rise to most of the preferred orientation observed.

WELL LOGS IN CARBONATE RESERVOIRS

Modern well logs can play an important, often decisive role in the evaluation of carbonate reservoirs, and in well completions therein. To do so however, the logs must be selected and interpreted with due regard for the specific rock “types” and pore structures encountered by each well. Indeed, the basic condition stated applies to all evaluation and completion techniques now in use or conceivable. It becomes vitally important in carbonate reservoirs, however, because of their extraordinary heterogeneity. Characteristically, these reservoirs exhibit significant, often extreme, and always unpredictable variations in pore structure, pore size distribution and fluid content, within very short distances, in any direction. To cope with such a reservoir, an evaluation and logging program adhering to certain principles is most likely to yield valid results and insure better completions and greater ultimate recovery, at minimum cost. First, in every well, the cuttings or cores should be described precisely as to rock types and depths. Second, any techniques used should permit the largest possible number of determinations through the reservoir, so that any existing relationships between pore size distribution, porosity and water saturation may be established on a sound statistical basis. Among logging devices, “focusing” tools meet this requirement best. Third, starting very early in the development of the reservoir, the latter should be cored and logged in key wells, the cores subjected to capillary pressure and other petrophysical tests, and all potentially diagnostic logs run and analyzed in the light of all other data. Fourth, in non‐key wells, the logging program should include only those logs proved most reliable in the key wells for the pore structures encountered and the data desired (usually porosity, water saturation, net ft of pay).