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.

Dynamics of water injection in an oil-wet reservoir rock at subsurface conditions: Invasion patterns and pore-filling events

Abstract: We use fast synchrotron x-ray microtomography to investigate the pore-scale dynamics of water injection in an oil-wet carbonate reservoir rock at subsurface conditions. We measure, in situ, the geometric contact angles to confirm the oil-wet nature of the rock and define the displacement contact angles using an energy-balance-based approach. We observe that the displacement of oil by water is a drainagelike process, where water advances as a connected front displacing oil in the center of the pores, confining the oil to wetting layers. The displacement is an invasion percolation process, where throats, the restrictions between pores, fill in order of size, with the largest available throats filled first. In our heterogeneous carbonate rock, the displacement is predominantly size controlled; wettability has a smaller effect, due to the wide range of pore and throat sizes, as well as largely oil-wet surfaces. Wettability only has an impact early in the displacement, where the less oil-wet pores fill by water first. We observe drainage associated pore-filling dynamics including Haines jumps and snap-off events. Haines jumps occur on single- and/or multiple-pore levels accompanied by the rearrangement of water in the pore space to allow the rapid filling. Snap-off events are observed both locally and distally and the capillary pressure of the trapped water ganglia is shown to reach a new capillary equilibrium state. We measure the curvature of the oil-water interface. We find that the total curvature, the sum of the curvatures in orthogonal directions, is negative, giving a negative capillary pressure, consistent with oil-wet conditions, where displacement occurs as the water pressure exceeds that of the oil. However, the product of the principal curvatures, the Gaussian curvature, is generally negative, meaning that water bulges into oil in one direction, while oil bulges into water in the other. A negative Gaussian curvature provides a topological quantification of the good connectivity of the phases throughout the displacement.

Detection of Pay Zones and Pay Quality, Gulf of Mexico: Application of Geochemical Techniques

Abstract: Testing of stacked-sand pay zones in the Gulf of Mexico (GoM) and other basins with similar depositional systems (e. g., offshore Nigeria, Bohai Bay) is quite costly when up to 11 sands need to be evaluated in order to determine testing and completion intervals. Other reservoir types such as fractured shale, carbonate, and fresh water reservoirs present challenging interpretation problems as well, especially in terms of assessing native hydrocarbon quality prior to testing and completion. With high daily rig rates and test costs, the ability to minimize idle time and testing expenses has direct economic impact on the cost of operating a well. In addition, identifying any potential bypassed pay zones provides additional economic benefit. A variety of potential pay zone types is present in the GoM ranging from biogenic, thermogenic dry gas, wet gas, or condensate to normal, heavy, waxy, or biodegraded crude oils. Assessment of GoM sands is complicated by the fact that they are typically unconsolidated sediments and are often drilled with oil-based or synthetic muds, which make it difficult to evaluate the presence of reservoired hydrocarbons using conventional logging techniques. Simple and inexpensive geochemical analyses provide information on reservoir hydrocarbons directly from prospective reservoir rock samples in about 15 minutes, thereby enhancing well site decision-making processes. Geochemical analyses of frozen cuttings or sidewall core (SWC) samples confirm the presence of native hydrocarbons and provide an assessment of hydrocarbon type (gas or oil) and quality (e. g., GOR, viscosity, API gravity). The first goal of geochemical analyses for well site decision making is to identify or confirm prospective pay zones including any potential bypassed pay, in either water or oil-based mud systems. The second goal is to identify the likely type and quality of pay. Further, the comparison of condensates in rocks to produced fluids can be used to assess vertical fractionation of reservoirs, seal effectiveness, and for correlation or oil typing purposes. Finally, vertical connectivity of reservoirs, which may also play a role in completion decisions, can be assessed using these data.

Using 3-D Seismic Volumetric Curvature Attributes to Identify Fracture Trends in a Depleted Mississippian Carbonate Reservoir: Implications for Assessing Candidates for CO2 Sequestration

Abstract: The widespread Western Interior Plains aquifer system of the central United States provides a significant potential for sequestration of CO2 in a deep saline formation. In Kansas, several severely depleted Mississippian petroleum reservoirs sit at the top of this aquifer system. The reservoirs are primarily multilayered shallow-shelf carbonates with strong water drives. Fluid flow is strongly influenced by natural fractures, which were solution enhanced by subaerial karst on a Mississippian–Pennsylvanian regional unconformity. We show that three-dimensional (3-D) seismic volumetric reflector curvature attributes can reveal subtle lineaments related to these fractures. Volumetric curvature attributes applied to a 3-D seismic survey over a Mississippian oil reservoir in Dickman field, Ness County, Kansas, reveal two main lineament orientations, N45E and N45W. The northeast-trending lineaments parallel a down-to-the-north fault at the northwestern corner of the seismic survey and have greater length and continuity than the northwest-trending lineaments. Geologic analysis and production data suggest that the northeast-trending lineaments are related to debris-, clay-, and silt-filled fractures that serve as barriers to fluid flow, whereas the northwest-trending lineaments are related to open fractures that channel water from the underlying aquifer. The discrimination of open versus sealed fractures within and above potential CO2 sequestration reservoirs is critical for managing the injection and storage of CO2 and for evaluating the integrity of the overlying seal. Three-dimensional seismic volumetric curvature helps to locate fractures and is a potentially important tool in the selection and evaluation of geologic sequestration sites.