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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.
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01 Jan 1998
TL;DR: In this article, a new constitutive model of the Ekofisk field's rock mass behavior consisting of two sets of 'end member' stress strain curves is presented. But the model assumes that the rock mass behaves as an assemblage of dominantly elastic, low compressibility matrix blocks capable of moving independently of neighboring blocks.
Abstract: The Ekofisk Field, a giant North Sea oil field, has produced more than 1.2 billion barrels of oil since the start of production in 1971. Sea floor subsidence, which was discovered late in 1984, has occurred at approximately a constant rate of about 38 cm/year since then. Full field water flooding began in 1987. Over the past decade numerous, long term laboratory studies of reservoir chalks were undertaken to understand the effects of water flooding on chalk strength and to provide input data for reservoir simulators and geomechanics codes used to predict reservoir compaction and sea floor subsidence. Recent laboratory analyses suggest that some protective mechanism, possibly oxidized, polar hydrocarbons adhering to portions of the chalk matrix, may protect the calcite matrix from intimate chemical interaction with formation brines. This observation has led to a new constitutive model of Ekofisk rock mass behavior consisting of two sets of 'end member' stress strain curves. The first set represents the reservoir rock prior to water flood invasion, when the rock mass behaves as an assemblage of dominantly elastic, low compressibility matrix blocks capable of moving independently of neighboring blocks. The second set represents fully water-contacted, fully water-weakened chalk that has undergone the transition from elastic to plastic behavior. In its fully water-weakened state the chalk is highly compressible and displays the high strain rates and large strains observed in water flooded intervals of the Ekofisk reservoir. The two sets of stress/strain curves are related by water saturation.
21 citations
TL;DR: Yutkin et al. as discussed by the authors showed that carbon-dioxide content of a carbonate reservoir, originating from CO2-rich crude oil and gas, plays a dominant role in setting aqueous pH and speciation.
Abstract: Author(s): Yutkin, MP; Lee, JY; Mishra, H; Radke, CJ; Patzek, TW | Abstract: © Copyright 2016, Society of Petroleum Engineers. Low-salinity waterflooding (LSW) is ineffective when reservoir rock is strongly water wet or when crude oil is not asphaltenic. Success of LSW relies heavily on the ability of injected brine to alter surface chemistry of reservoir rock-brine-crude oil interfaces. LSW in carbonate reservoirs is especially challenging because of high brine salinity and, more importantly, because of high reactivity of the rock minerals. Here, we tackle the complex physicochemical processes in chemically active carbonates flooded with diluted brine that is saturated with atmospheric CO2 and possibly supplemented with additional ionic species, such as sulfates or phosphates. Later work will focus on the important role of crude oil and multicomponent ion-exchange (MIE) in LSW. When waterflooding carbonate reservoirs, rock equilibrates with the injected brine over short distances. Injected-brine ion speciation is shifted substantially in the presence of reactive-carbonate rock. Our new calculations demonstrate that rock-equilibrated aqueous pH is slightly alkaline quite independent of injected-brine pH. We establish, for the first time, that carbon-dioxide content of a carbonate reservoir, originating from CO2-rich crude oil and gas, plays a dominant role in setting aqueous pH and speciation. A simple ion-complexing model predicts calcite surface charge as a function of composition of reservoir brine. The surface charge of calcite may be positive or negative depending on speciation of reservoir brine in contact with the calcite. There is no single point of zero charge; all dissolved aqueous species are charge determining. Rock-equilibrated aqueous composition controls calcite surface ionexchange behavior. At high ionic strength, the electrical double layer collapses and is no longer diffuse. All surface charges are located directly in the inner and outer Helmholtz planes. Our evaluation of calcite bulk and surface equilibria is preliminary but draws several important inferences about proposed LSW oil-recovery mechanisms. Diffuse double layer expansion (DLE) is not possible unless brine ionic strength is below 0.1 molar. Because of rapid rock/brine equilibration, the dissolution mechanism for releasing adhered oil is eliminated. Also, fines mobilization and concomitant oil release cannot occur because there are few loose fines and clays in a majority of carbonates. LSW cannot be a low interfacial-Tension alkaline flood because carbonate dissolution exhausts all injected base near the wellbore and lowers pH to that set by the rock and by formation CO2. In spite of diffuse double-layer collapse in carbonate reservoirs, surface ion-exchange oil release remains feasible, but unproven.
21 citations
TL;DR: Yacheng 13-1 is the largest gas field in China's offshore region, with proven initial in place gas and condensate reserves around 98.2 billion cubic meters (bcm) and 3.74 million cubic meters(mcm) respectively as mentioned in this paper.
21 citations
TL;DR: The interpretation of the experimental results and the approach the authors have adopted for extrapolating them to field conditions are discussed, so that the reservoir engineer can assess their practical consequences for field development.
Abstract: When a waterflooded oil reservoir is to be depressurized, it is important to predict the production of solution gas from the by-passed and trapped oil. To quantify the gas saturation build-up and the relation between gas mobility and gas saturation, the authors have carried out a large number of experiments on core samples. In this paper the authors discuss the interpretation of the experimental results and the approach the authors have adopted for extrapolating them to field conditions, so that the reservoir engineer can assess their practical consequences for field development. They found that when the experiments were run starting under initial reservoir conditions, the nucleation properties of the fluid/rock/pressure combination, together with the depletion rate, determine the gas saturation build-up. To extrapolate such laboratory results to the pressure-decline rate of the field, it is essential that the experiments be conducted with reservoir fluids at reservoir pressure and temperature. When the experiments were run under watered-out conditions, no such dependency on nucleation properties was found. Instead, the mobility of the gas could be correlated with the total hydrocarbon saturation, the same correlation applying to different fluid/rock/pressure combinations.
21 citations
TL;DR: The branch of petroleum engineering concerned with predicting the optimum economic recovery of oil fields is the branch of Petroleum Engineering (PE) as discussed by the authors, a branch of the field of economics concerned with prediction of economic recovery.
Abstract: The branch of petroleum engineering concerned with predicting the optimum economic recovery of oil o…
21 citations