Oil and Gas

Biography

Biography: Vahora Shahenazbanu Altafbhai

Abstract

Petro physics is the study of physical and chemical rock properties and their interactions with fluids. The most petro physicists work in the hydrocarbon industry, some also work in the mining and water resource industries. The properties measured or computed fall into three broad categories: conventional petro physical properties, rock mechanical properties, and ore quality. Some of the key properties studied in petro physics are(1) litho logy, (2)porosity, (3)water saturation,(4) permeability and(5) density. A key aspect of petro physics is measuring and evaluating these rock properties by acquiring well log measurements - in which a string of measurement tools are inserted in the borehole, core measurements - in which rock samples are retrieved from subsurface, and seismic measurements. These studies are then combined with geological and geophysical studies and reservoir engineering to give a complete picture of the reservoir. Properties of petro physics: (1)Litho logy: A description of the rock's physical characteristics, such as grain size, composition and texture. By studying the litho logy of local geological outcrops and core samples, geoscientists can use a combination of log measurements, such as natural gamma, neutron, density and resistivity, to determine the litho logy down the well. (2)Porosity: The percentage of a given volume of rock that is pore space and can therefore contain fluids. This is typically calculated using data from an instrument that measures the reaction of the rock to bombardment by neutrons or by gamma rays but can also be derived from sonic and NMR logging. (3)Water saturation: The fraction of the pore space occupied by water. This is typically calculated using data from an instrument that measures the resistivity of the rock and is known by the symbol . (4)Permeability: The quantity of fluid (usually hydrocarbon) that can flow through a rock as a function of time and pressure, related to how interconnected the pores are. Formation testing is so far the only tool that can directly measure a rock formation's permeability down a well.[citation needed] In case of its absence, which is common in most cases, an estimate for permeability can be derived from empirical relationships with other measurements such as porosity, NMR and sonic logging. (5) Density: Density is a function of composition, porosity and saturation .Density is calculated from mass and volume measurements. Mass is determined by carefully weighing the sample on an analytical balance. For irregular shaped samples, volume is usually based on Archimedes’s principle. The stereo pycnometer determines volume based on the displacement of gas. Application of petro physics: (1)The determination of litho logy, net pay, porosity, water saturation, and permeability from wellbore core and log data. The chapter deals with "Development Petro physics" and emphasizes the integration of core data with log data; the adjustment of core data, when required, to reservoir conditions; and the calibration and regression line-fitting of log data to core data. The goal of the calculations is to use all available data, calibrated to the best standard, to arrive at the most accurate quantitative values of the petro physical parameters (i.e., lithology, net pay, porosity, water saturation, and permeability). Log analysis, cased-hole formation evaluation, and production logging are not covered here. (2) Petro physical data sources and databases, litho logy determination, net-pay determination, porosity determination, fluid-contacts identification, water-saturation determination, permeability calculations, case studies, other considerations in petro physical calculations, and summary and conclusions. It does not cover the propagation of the wellbore values, or "populating" of static or dynamic reservoir models, vertically and a really over the whole of the reservoir volume.