That is, for small strains, the elements of the stress and strain tensors are related through where Furthermore, the strain response occurs instantaneously as soon as the stress is applied, and it is reversible—that is, after removal of a load, the material will be in the same state as it was before the load was applied.
Various light minerals impact the density, neutron, and sonic logs, like: Coal Various radioactive minerals impact the GR log, such as: Uranium Potassium salts such as K-feldspar Various electrically conductive minerals impact the resistivity logs, like: Clay minerals Pyrite Clay-mineral properties Clay minerals are, in general, composed of layered alumina and silicate molecules,    and the properties of the various clay minerals vary widely.
Some swell when wet, are plastic, and can easily deform, while others are hard and dense. Clay minerals are extremely fine-grained, and those with the smallest grain size have a very high surface-area-to-volume ratio. However, it is the smectites one of which is montmorillonite that often cause very significant effects on the petrophysical measurements of porosity and water saturation.
In smectites, exchange cations and adsorbed water molecules are loosely bound between the silicate layers. Dehydration occurs whenever there is low humidity or an elevated temperature e. Loss of this adsorbed water is even more rapid at temperatures above the boiling point of water.
For smectites, this is a problem during core analysis because the extraction and drying of the core samples is an essential step in the measurement procedures.
For resistivity logging, smectite clay minerals pose a further problem. The exchange cations and adsorbed water molecules lead to smectite exhibiting excess electrical conductivity. This occurs as exchange cations e.
The clays thus exhibit a lower resistivity and, in most cases, depress the bulk resistivity of reservoir rocks in which they reside. Cation exchange also occurs with the other clay minerals, but to a lesser extent.
Rock formations of pure clay minerals are rare. More typically, several species of clay mineral are associated together with clay-sized and silt-sized quartz, mica, and other rock grains. This association is known widely as "shale.
Besides the adsorbed water on the clay minerals, shales and authigenetic clay minerals also include additional formation water held in their micron-sized pore system by capillary retention.
This water cannot be produced from the formation and is referred to as "capillary water. The net result is that water is expelled from the shale beds into surrounding permeable beds. Young clay-mineral-bearing sediments at shallow burial depths are likely to be smectites e.
Clay minerals in deeply buried shales become less hydrated, and their forms can be altered by higher temperatures and pressures. Low-salinity water is sometimes observed in reservoir-rock pores adjacent to the shales and where clay-mineral-expelled water cannot escape from the permeable bed.
This formation may become overpressured and can cause severe problems during drilling if not predicted or detected in time to alter the drilling program. Although shale formations are not usually of commercial importance, the measurement and evaluation of core and log data in partly shaly reservoirs presents many difficulties that are not present in clay-mineral-free clean formations.
A large body of technical literature addresses shaly-formation analysis because the shale, to one degree or another, affects all log and core measurements. Because these shaly rocks are so variable, a single model usually cannot fully describe all of their behaviors.
Each represents short periods of deposition where the suspended finest sediments could settle out of the original sediment-rich river, lake, or seawater.
Laminated shales may range from approximately one hundredth of a centimeter to 1 m thick. Shale deposits can be broken up and reworked after their original deposition and become "grains" in the same manner as quartz grains. Structural, or detrital, shale grains become a part of the grain composition of sandstone.
As well as the clay minerals that are deposited directly as solids from lakes and marine environments, they also may be deposited from in-situ formation-water solutions that are rich in dissolved minerals.
These clay minerals are called "authigenetic. Of this type, illite, kaolinite, chlorite, and smectite clays are most common. Each can take several physical and chemical forms within a pore. Several generations of pore-filling clay minerals may be present, representing different periods of geological time when changes occurred in formation-water composition or depth of burial.
Evaluation of shale volume Geological techniques, like XRD, are available to identify clay-mineral species and to quantify rock-component volumes in physical specimens.
Such analyses can help calibrate the log-based methods for estimating Vsh, the bulk-volume fraction of shale. Vsh from the GR log is frequently used to determine nonpay. Shale content can be estimated from well logs by many techniques, because shale affects the readings of most logs.
The task for a particular field is to identify an evaluation technique that is reasonably accurate and as simple as possible. A method using a combination of the neutron and density logs is often applied for practical log analysis.The petroleum reservoir 1 Significance of rock properties 1 Chapter 2.
POROSITY 3 Definition 3 Types of porosity 6 Resisitivity log 25 Chapter 6. ROCK PERMEABILITY 28 properties determine the total volume of petroleum in the trap; others limit the fraction of. A petroleum reservoir or oil and gas reservoir is a subsurface pool of hydrocarbons contained in porous or fractured rock monstermanfilm.comeum reservoirs are broadly classified as conventional and unconventional reservoirs.
In case of conventional reservoirs, the naturally occurring hydrocarbons, such as crude oil or natural gas, are trapped by overlying rock formations with lower permeability. Petrophysical Rock Typing: Enhanced Permeability Prediction and Reservoir Descriptions* Wanida Sritongthae1.
Search and Discovery Article # ()**. Re-Evaluation of Bottom-Hole Temperature Corrections - New Insights from Two Wells in West Central Utah, Rick Allis and Mark Gwynn, # ().. Leveraging Digitization to Achieve Operational Certainty, Pattabhiraman Ganesh, # ().. PS Application of Mercury Injection Capillary Pressure to Mudrocks: Conformance and Compression Corrections, Sheng Peng, Tongwei Zhang, and Robert.
o Perturb reservoir properties using rock physics effective medium models (pseudo-well o Create graphics and digital output files. Geophysical Well Log Analysis Well log analysis for geophysics differs in several important ways from standard log analysis. Well Logs and Rock Physics in Seismic Reservoir Characterization; Walls, Dvorkin.
The main objective of carbonate reservoir formation evaluation is to determine the reservoir storage capacity, flow capacity, mineralogy and mechanical rock properties while honoring physical data measurements. Key well studies that incorporate conventional core analysis and wireline log analysis assist in determining these factors for.