Architectural Controls on the Recovery of Hydrocarbons From Sandstone Reservoers

Abstract

Development of the 330-billion-bairel oil resource remaining in United States reservoirs after conventional primary and secondary recovery will be dependent on the advanced understanding of facies relations and compartmentalization inherent in reservoir depositional systems. Style of deposition, as reflected in internal reservoir architecture, defines flow units that determine how a reservoir drains, where hydrocarbons remain unrecovered at the interwell (macroscopic) scale, and what approaches will be effective in accessing unrecovered oil. A substantial part of the unrecovered oil resource is nonresidual oil that, although mobile in the reservoir, remains unrecovered owing to poor contact by existing wells and vertical or areal bypassing by the waterflood front. Because heterogeneity style is a product of depositional system, it is predictable and can be characterized in terms from low to high in a lateral and vertical sense. For sandstones, the wave-dominated deltas, barrier cores, and sand-rich strand plains show a low degree of heterogeneity in both dimensions, whereas the highly aggradational backbarrier fans, fluvially dominated deltas, and fine-grained meander belts show a higher intensity of heterogeneity. Other systems can be similarly classified. The resulting matrix leads to delineation of targeted approaches to incremental oil recovery specifically tailored to the distribution of remaining oil saturation. Such approaches, optimized to the character of the depositional system, may include geologically targeted infill drilling, selective recompletion, horizontal drilling, and strategic cross-reservoir flooding involving flood redesign and profile modification. Such techniques are herein termed Advanced Secondary Recovery (ASR) and represent advancements in technology that will lead to near- and mid-term improvements in efficiency that set the stage for later approaches to Enhanced Oil Recovery (EOR).

EOR Potential from CO2 Captured from Coal-Fired Power Plants in the Upper Cretaceous (Cenomanian) Woodbine Group, East Texas Basin, and Southeastern Texas Gulf Coast, USA

“…Oakwood Dome is located within the axis of a deltaic depocenter with sandstone-rich distributarychannel deposits, whereas OSR field produces from off-axis delta-front facies. Recovery efficiencies in fluvial-dominated deltaic reservoirs such as those in Mapleton, Navarro Crossing, Oakwood Dome, and OSR fields are typically only 20-40% of OOIP (Tyler et al 1984;Tyler and Finley 1991).…”

“…In a review of $450 oil reservoirs in Texas, Tyler et al (1984) and Tyler and Finley (1991) described relationships between depositional systems, recovery efficiency, and oilrecovery potential. Reservoirs of deepwater origin are heterogeneous, with <25% recovery efficiency.…”

Identifying Viable EOR Thermal Processes in Canadian Tar Sands

“…Additionally, the impact of large-scale geological heterogeneities associated with the recovery of oil has been documented and shows a relationship between the architecture of the sandstone reservoir, conventional recovery efficiency, and EOR strategies [8,9] . The proposed approach is a matrix based on the geological depositional systems that have been characterized based on their inherent lateral and vertical heterogeneities.…”

“…If the dimensions of sand bodies, or genetic units (length, thickness, and width), current or proposed well length, and well spacing are known, horizontal and vertical heterogeneity indexes can be estimated using simple equations documented in the literature [8,9] . Based on this approach, heterogeneity indexes are first estimated between two horizontal wells where the flow between the wells is vertical (e.g.…”

MPS-Driven Digital Rock Modeling and Upscaling

“…Heterogeneity indicates the variation of a rock property in space while anisotropy reflects the variation of the property with the direction in which it is measured (Tyler and Finley 1991;Anderson et al 1994). Both heterogeneity and anisotropy are intrinsic reservoir rock characteristics that are mainly governed by the origin of the source materials and the sedimentary as well as the diagenetic processes.…”