George V. Chilingar

Prediction of Abnormally High Formation Pressures (AHFP) in petroliferous salt-bearing sections

Abstract Prediction of overpressures [Abnormally High Formation Pressures (AHFP)] in the evaporite sequences is indeed a challenging problem. Several techniques are suggested here for the solution of this forecasting problem. For a reliable AHFP forecast it is necessary to delineate the salt plugs. A method of accomplishing this is presented here. In many cases there is evidence of vertical gas migration along flanks of salt plugs and associated fractured zones (and faults). The composition of gases in the secondary traps in the sealing evaporite sequence is the same as that of gas in the massive, major accumulation below. Predictive precursors of the AHFP include lithological barrier (e.g., anhydrite) with decreasing drilling rates and appearance of “gas clay” in circulating mud (i.e., plastic greenish-gray and brown clay with gas bubbles).

Experimental Design in Petrophysical Studies: Passive and Active Petrophysical Experiments

This article describes examples of experimental design, which is the procedure and pattern for obtaining mathematical description or mathematical model of a process or parameter under study as linear or nonlinear regression equation based on the limited number of reproducible experimental data. The examples are related to petrophysical studies of the influence of clay and carbonate contents in clastic rocks and depth of burial on porosity (passive experiment), and the influence of temperature and pressure on some principal petrophysical parameters (active experiment).

Why many overpressured, stress-sensitive hydrocarbon reservoirs should not be abandoned

Most commercial oil sands exhibit shale resistivity ratios (ratio of normal R shn to observed R sho ) of less than approximately 1.6 in adjacent shales and can be reached without an expensive string of protection pipe. On the other hand, some experts claim that “no commercial production is found when the shale resistivity ratio reaches and/or exceeds 3.5.” This statement, however, needs further investigation Such wells often are highly productive initially and are characterized by extremely fast pressure depletion. Based on extensive compaction studies of rocks, the authors argue that the latter is due to plastic deformation (irreversible compaction) in undercompacted overpressured rocks with increasing effective stress soon after production is initiated (or during well testing). Thus, well tests could be quite misleading, and many er roneously condemned overpressured reservoirs should be reexamined, reevaluated, and strategies be developed to recover the oil and gas from these stress-sensitive reservoirs.

Why the Probability of Finding Highly-Organized Life (as it Exists on Earth) on Another Planet in Our Galaxy is Very Low

Abstract The evolutionary path of Earth was predetermined by solar luminosity, its position in the solar system, and its mass and chemical composition. All these variables were favorable for the development of highly-organized life on Earth.

Experimental Design in Petrophysical Studies: Fundamentals

This article describes the basic principles of experimental design, which is the procedure and pattern for obtaining mathematical description or mathematical model of a process or parameter under study as linear or nonlinear regression equation based on the limited number of reproducible experimental data. Experimental design in petrophysical studies is applied to investigate, for example, the influence of clay and carbonate contents in clastic rocks and depth of burial on porosity and permeability, and the influence of temperature and pressure on some principal petrophysical parameters.

Petrophysical Simulation in Petroleum Geology and Reservoir Engineering

The simulation of multivariate petrophysical relationships between core and well-log derived parameters on the example of the South Caspian Basin is discussed. For developing the petrophysical relationships, a number of deterministic and stochastic calculating procedures are used by the authors. These relationships are widely used in petroleum geology and reservoir engineering for hydrocarbon reserves estimation, reservoir description and simulation, field development planning, and reservoir production management.

Prediction of Hydrocarbon Reservoir/Trap Type in Stratified Sedimentary Deposits

The recognition of traps most likely to contain hydrocarbons, while making reconnaissance surveys or at an early stage of exploration, has never been an easy task. Utilizing mathematical indicators can allow the identification of likely traps containing oil and/or gas accumulation during early exploratory drilling programs. The guidelines set forth in this article permit one to refine the exploration and delineation operations and focus exploration efforts on only those traps that are most likely to contain economic hydrocarbons. This “focusing” saves valuable time and economic resources.

Axiomatic Approach to the Geological and Geophysical Sciences

This article describes the basic principles of an axiomatic approach to investigations in the area of the Earths science and provides examples of implementation of these principles, namely, in the areas of geophysical investigations and formation pressure evaluation and prediction, including abnormally-low and abnormally-high pressures.

CHAPTER 11 – Mathematical Modeling of Geological Processes (Dynamic Geological Systems)

The chapter, using numerical simulation, shows that modeling coefficients adequately represent the influence of many geological factors on the petrophysical properties of rocks that in turn signifies that the reservoir properties of Mesozoic and Neogene rocks are very different. The chapter also highlights that geological time is the main factor determining the degree of rock compaction. By comparing the results obtained by the simulation of clastic reservoir rock properties, such as sandstones, with those of carbonate rocks, the chapter explains that the carbonate rocks become compacted and consolidate faster than the sandstones. The results of the numerical simulation also indicated that statistical distributions of porosity and density obey the normal law, whereas the distribution of permeability obeys the lognormal law. The chapter presents a multivariable model of lithification of both terrigenous and carbonates sediments in rocks. This model is an integral part of the models used for predicting the properties, such as porosity, permeability, and bulk density, of oil and gas bearing rocks. The relationships between absolute and normalized values of geologic factors are established on the basis of these experimental and field data, using which the chapter proposes models for the evaluation of both reservoir rock and caprock properties. The chapter also presents software for the calculation of rock properties, and then calculates the reservoir rock and caprock properties at reservoir temperature and pressure using both the computer program and the proposed models. The chapter also verifies the proposed method of numerical simulation of oil and gas bearing rock properties using numerous examples.

CHAPTER 8 – Conclusions (Chapters 1 to 7 Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7)

The chapter uses conclusions of previous chapters, and briefly describes characteristics of the oil and gas bearing formations in the South Caspian basin. The main oil and gas bearing formation in the Eastern Azerbaijan and the offshore areas of Apsheron and Baku archipelagoes is in the middle Pliocene productive series, based on the characteristic mineral composition of both light and heavy minerals. The productive series is separated into two divisions, lower and upper, and into several suites according to lithology. Core data, paleontological studies, and log response suggest that sediments of the productive series were deposited in a shallow-water, fluvial-deltaic environment. The productive series is again divided into seven sedimentary sequences according to the transgression and regression cycles during the basin development. Reservoir-rock properties of the productive series, which are very good, vary both within the section and over the area. Paleogene to Neogene argillaceous rocks, which are widespread in the geologic section of the Azerbaijan and the South Caspian basin, make up to 50 to 95% of the section and play a key role in establishing lithologic, mineralogical, geochemical, and thermobaric characteristics of the basin. Undercompaction of argillaceous rocks, even at depths down to 6.5 km, is explained by the comparatively young age, a high sedimentation rate, their great thickness, and incomplete squeezing-out of pore water. Development of abnormally high-pore pressures may lead to the lateral variation of rock density, and under certain geologic conditions to folding, clay diapirism, mud volcanism, and earthquakes.