Petroleum reservoir

About: Petroleum reservoir is a research topic. Over the lifetime, 5403 publications have been published within this topic receiving 83535 citations. The topic is also known as: petroleum deposit.

Predicting rock mechanical properties from wireline porosities

Abstract: The rock mechanical behaviour of reservoir rocks is important in the design and implementation of drilling and production programmes. Traditionally rock mechanical properties are obtained from direct measurement on core samples or from mechanical calculations on acoustic wireline log measurements. This paper reports the rock mechanical properties of many different reservoir rocks of different porosities. This has led to the development of a new method of predicting rock mechanical properties directly from porosity. The paper discusses the measurement of experimentally derived porosity, elastic moduli and fracture strength parameters and the interpretation of these mechanical properties results into direct correlations with porosity. The application of these results to obtain continuous rock mechanical property plots of the reservoir from wireline derived porosity is discussed. The practical use of these rock mechanical property profiles in drilling, production and enhanced reservoir simulation is also emphasised. Porosity (Φ), modulus of elasticity (E), Poisson's Ratio (ν), uniaxial compressive strength (UCS), cohesion (τ 0 ), angle of internal friction (ψ), and triaxial stress factor (k), were measured on samples from a wide range of North Sea reservoirs using a conventional triaxial testing machine. This paper describes the procedure used and presents the correlations obtained from plotting each of the rock mechanical properties against porosity. The derivation of wireline porosities along with empirical corrections are presented and the results of applying the correlations to these wireline derived porosities to produce continuous rock mechanical property plots are discussed. Logs were calibrated to core-measured values to reveal realistic elastic and inelastic moduli profiles. The continuous property logs provide a reasonable estimate of the possible behaviour at discrete points throughout the reservoir interval, but they are limited in their description of the behaviour of individual beds as coherent bodies. A technique has been developed to pick out these individual beds and assess how they will perform as Rock Mechanical Coherent Units, i.e. sets of beds that perform in a similar or dissimilar manner to adjacent layers. Finally a discussion on how the results are used to aid production and generate enhanced reservoir simulation will be presented.

Simulation Model for Petroleum Exploration

Abstract: A computerized simulation model was constructed to synthesize the processes of petroleum generation, migration, and accumulation under relatively simple conditions. The model successfully simulated accumulation in an existing anticlinal gas field, and was used to estimate the possibility of fault and stratigraphic entrapment nearby. The geologic cross section of the area is divided into a series of vertical columns, which are sectioned into rectangular cells representing successive intervals of time and the strata deposited therein. Four geologic processes are sequentially performed on each cell or on each pair of adjacent cells: (1) deposition, (2) compaction, (3) petroleum generation, and (4) petroleum migration. First, sediment is deposited in the cell, with its original thickness restored by removing the effects of compaction. Then for each time-stratigraphic unit, the system calculates the amount of compaction caused by increasing time and depth of burial, and also the amount of petroleum generated, which is assumed to be a function of temperature. Primary migration is assumed when the petroleum saturation o the shale source beds exceeds the residual amount normally in thermally mature shale. Secondary migration is assumed to result from buoyancy alone; any petroleum which exceeds the hydrostatic trapping capacity of the shale seal migrates into a cell located along some upward path or escapes to the surface. The model was applied to the anticlinal East Niigata field, Japan, using carefully selected input parameters. Results made it possible to estimate the migration paths and the timing of entrapment in each producing zone under the assumed conditions. The model may also be applied to exploration problems. It was used to estimate the possibility of petroleum entrapment in homoclinal strata near the East Niigata field under several assumed geologic situations. Results of this experiment show that the simulation method is potentially very useful for estimating the possibility and places of entrapment, especially for stratigraphic traps.

Relationships of Source Rock, Thermal Maturity, and Overpressuring to Gas Generation and Occurrence in Low-Permeability Upper Cretaceous and Lower Tertiary Rocks, Greater Green River Basin, Wyoming, Colorado, and Utah: ABSTRACT

Abstract: Most hydrocarbon production from low-permeability Upper Cretaceous and lower Tertiary reservoirs in the Greater Green River basin of Wyoming, Colorado, and Utah is gas. The most likely sources of the gas are the interbedded coal beds and other carbonaceous lithologies. A source-rock evaluation of these rocks indicates predominantly humic, type III organic matter capable of generating mainly gas. The relatively closed nature of these low-permeability rocks facilitates examination of the geologic processes involved in gas generation and occurrence. All gas accumulations are associated with overpressuring. Thermal generation of gas is the main cause of overpressuring and is directly related to organic richness, level of organic maturation, and temperature. Distances of gas migration, in most areas, do not exceed a few hundred feet. Consequently, the temporal relationships of gas generation and migration with respect to the development of structural and stratigraphic traps are not as important as in more conventional reservoirs. On the basis of the premise of minimal gas migration, the initiation, or threshold of significantly large volumes of thermogenic gas occurs at a temperat re of about 190°-200°F (88°-93°C) and a vitrinite reflectance of about 0.80 Ro. End_of_Article - Last_Page 940------------

Models of Porosity Formation and Their Impact on Reservoir Description, Lisburne Field, Prudhoe Bay, Alaska

Abstract: The Lisburne field at Prudhoe Bay, Alaska, produces from shelfal carbonates in the Pennsylvanian Wahoo formation. Four major factors control reservoir behavior: (1) depositional stratification, (2) a fractured, permeable subunconformity alteration zone (SAZ), (3) multiple episodes of porosity formation, and (4) faulting. This paper is the first written description of facies, cyclicity, and diagenetic processes as they apply to porosity formation and reservoir modeling in the Lisburne field. Successive depositional cycles in the Wahoo formation pass from ooid/skeletal grainstones deposited in shoal complexes to oncolitic packstones and skeletal/peloidal wackestones formed in restricted lagoonal environments. Geochemical data and crosscutting relationships between porosity and unconformities, pressure solution features, fractures, and faults provide evidence of three distinct episodes of porosity formation. Earliest porosity is probably due to periodic, localized exposure during the Pennsylvanian. A second stage of porosity is associated with shallow-burial dolomitization that probably began during Permian-Triassic subaerial exposure. Reservoir quality in dolomites varies with the degree of neomorphic recrystallization. The third stage began in the Cretaceous and lasted in o the Tertiary, and is associated with final burial and hydrocarbon maturation. This burial dissolution event also opened existing fault systems, creating a complex reservoir. Most Lisburne field effective porosity is of late-burial origin due to either dolomitization or dissolution. Faults and the SAZ act as giant collectors of oil from low-permeability matrix, and they have reduced the number of wells needed for field development. Faults also complicate waterflood implementation and maintenance of uniform reservoir pressure. Field studies such as these demonstrate the importance understanding the diagenetic history of a reservoir can have for field management and development planning.