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.

Distribution of Hydrocarbons Between Oils and Associated Fine-Grained Sedimentary Rocks--Physical Chemistry Applied to Petroleum Geochemistry, II

Abstract: Amounts and ratios of hydrocarbons in nonreservoir rocks (potential source rocks) can be compared with associated oils if, in relatively old and stable geologic situations, the hydrocarbons reach or closely approach a distribution equilibrium between source rock and reservoir. A distribution-equilibrium equation makes possible the calculation of the composition of a hypothetical oil expected from the composition of the hydrocarbons in the nonreservoir rock and from the different tendencies of the hydrocarbons to be absorbed tendencies have been measured and the hypothetical oil compositions calculated and compared with those of the real oils. The hypothetical and actual oil compositions agree very well in some relatively old and deep sedimentary deposits in which the source rocks and associated oils probably are related genetically. On the other hand, there is relatively poor agreement in some relatively young and shallow deposits, but the agreement appears to improve with increasing depth and age. One explanation for this is that the hydrocarbons in the relatively young and shallow oils may not be related genetically to associated young and shallow source rocks, but came from older and deeper ones. Alternatively the hydrocarbons in the young and shallow reservoirs and in the associated source rocks, in fact may be related genetically, but do not appear to be in distribution equilibrium because primary migration is still o curring. These findings imply that certain petroleum components, particularly the saturated hydrocarbons, are generated and migrate over relatively long periods of time. The results also may imply that the generation of petroleum components in fine-grained sedimentary rocks causes primary migration. Perhaps it is unreasonable to assume that perfect equilibrium may be reached between source rock and reservoir, but this is the presupposition made when looking for close similarities in compositions of oils and rock extracts in order to correlate oils with source rocks.

Reservoir geochemistry: a link between reservoir geology and engineering?

Abstract: Geochemistry provides a natural but poorly exploited link between reservoir geology and engineering. The authors summarize some current applications of geochemistry to reservoir description and stress that because of their strong interactions with mineral surfaces and water, nitrogen and oxygen compounds in petroleum may exert an important influence on the PVT properties of petroleum, viscosity and wettability. The distribution of these compounds in reservoirs is heterogeneous on a sub-meter scale and is partly controlled by variations in reservoir quality. The implied variations in petroleum properties and wettability may account for some of the errors in reservoir simulations.

Capillary-based method for rock typing in transition zone of carbonate reservoirs

Abstract: Reservoir simulation is established as a good practice to make the best decision for a petroleum reservoir. The reservoir is characterized in terms of reservoir elements such as structural model, well data, rock and fluid properties. Then the reservoir model is enhanced through history matching and finally different prediction scenarios are tried to find the best plan for the reservoir understudy. The more accurate the reservoir is characterized, the faster and the more precisely the history match is finished and the more reliable predictions are obtained. The most important part of reservoir characterization is the rock typing, where the quality of CCAL (conventional core analysis) and SCAL (special core analysis) properties are evaluated and estimated for any simulation grid. The resulting oil in place must be confirmed by the OOIP (original oil in place) calculated based on average petro-physical parameters for any layer. To allocate different rock types to simulation grid, rock types should be assigned according to different ranges of rock differentiation parameter which has to be determined in any specific study. Based on our experience in Iranian carbonate reservoirs, most frequently irreducible water saturation is the rock differentiation parameter. In the oil zone, water saturation from log data is assumed to be the irreducible water saturation. Thus, the rock type is identified with no trouble. The problem arises in transition zone, where water saturation from log data is not equal to the irreducible water saturation of that rock. This study includes the observed variations in terms of water saturation data versus depth and how to assign rock types to the transition zone grids. The objective of the capillary-based method is to produce a water saturation map which honors laboratory data as well as the well log data and considers the depth so that it can handle the transition zone in a proper manner. In fact, novelty of this work is to explain how it is possible to consider log and capillary pressure data together so that the most accurate rock type is assigned to reservoir grids of the transition zone. Moreover, this method is consistent with equilibration method for initializing reservoir simulations. A procedure is presented for how to implement the capillary-based method in a stepwise manner. Once the proposed method is carried out, the initialized simulation model is consistent with all sources of data (core analysis and petro-physical data). In this procedure original oil in place calculated after the initialization for simulation is more accurate and can be cross-checked with volumetric calculation based on interpreted log data. Therefore, it is considered to facilitate subsequent stages of reservoir study, namely history match and prediction.

Flat spot exploration

Abstract: The hydrocarbon-brine contact produces a flat reflection, unconformable with the lithologic reflections from the trap boundaries, and over a limited area bounded by structural contours. When it can be reliably detected and mapped, the flat spot can provide (i) a reasonably unambiguous indication and areal extent of a reservoir and (ii) an estimate of reservoir thickness. The gas-brine contact in thick reservoirs in offshore elastic sections is the easiest target. An example of gas mapping is presented in the paper. Other reservoirs represent a continuum of increasingly elusive targets. Increasing the range of applicability of flat spot exploration will require (i) increases in signal/noise and multiple ratio, increases in the three dimensional depth point density (or grid density), increased resolution and static and dynamic correction accuracy, and (ii) processing and interpretation aimed directly at flat spot mapping. Low relief structural and stratigraphic traps should provide the most attractive targets. The approach should be at least theoretically feasible, though not necessarily cost effective, for most major reservoirs with a well-behaved hydrocarbon brine contact.