Using Geostatistical Inversion of Seismic and Borehole Data to Generate Reservoir Models for Flow Simulations of Magnolia Field, Deepwater Gulf of Mexico

Abstract

Study of key parameters of reservoir viz, porosity, water saturation, permeability and pore size distribution from well logging data is more complicated in carbonate reservoir due to geological heterogeneities than Clastic reservoir.The Magnolia field is located in GOM blocks GB 783 and 784 and produces from Plio-Pleistocene turbiditic sands that form a complex channel/levee sequence penetrated by 16 boreholes. The primary pays consist of two sands, each about 200 feet thick, separated by a 15 foot shale layer. The pays are divided into an eastern gas prone province and a western oil prone province. A reservoir flow simulation model is planned to optimize production from existing wells and to facilitate future field development. Construction of an accurate model is complicated by MDT pressure measurements which indicated compartmentalization below the resolution of conventional seismic analysis, and by overlap of the seismic attributes derived from producing reservoirs, wet sands, and shales.To mitigate these factors, geostatistical inversion was chosen to produce the rock property inputs for the flow simulation models. This approach allowed development of a rock properties model consistent with core data, log data, and geologic constraints as well as seismic information. It also allowed assessment of uncertainty through the generation of a statistically significant number of internally consistent alternate solutions (realizations). A Markov Chain Monte Carlo method was employed to integrate borehole and geologic information to produce acoustic impedance and lithology volumes which were then used to co-simulate porosity, permeability, p-wave velocity, and water saturation volumes. Multiple realizations of these products were reviewed, uncertainty was assessed, and a rock properties model was selected for conversion to a flow simulation modeling format. The entire process can be rerun relatively quickly to accommodate additional wells and improved seismic data or to match production history.

Fluid overpressure as a control on sandstone reservoir quality in a mechanical compaction dominated setting: Magnolia Field, Gulf of Mexico

“…This is supported by the diverse values of overpressure that have been recorded in different reservoir units (Fig. ) and by fluid geochemical data which showed heterogeneous and unmixed reservoir fluids (Weissenburger and Borbas, ; McCarthy et al ., ). In the case of highly overpressured sand units, the presence of stratigraphic flow barriers such as thick mudstone units will have provided adequate seals for the efficient trapping of pore fluids and hence overpressure development (Fig.…”

Climbing‐ripple successions in turbidite systems: depositional environments, sedimentation rates and accumulation times

“…Seismic and borehole data indicate that the reservoir is heterogeneous and includes thick, blocky sandy turbidites, mass transport deposits and thinner bedded CRCL‐rich successions. Furthermore, fluid pressure, phase and compositional data indicate that the reservoir is highly segmented and compartmentalized (Weissenburger & Borbas, 2004; McCarthy et al. , 2005, 2006) due to syn‐depositional and post‐depositional faulting due to allochthonous salt movement.…”

“…Furthermore, CRCL are commonly deposited in off‐axis depositional environments where significant amounts of mud also accumulate between events. These factors, combined with fault‐related heterogeneity, have led to the intense compartmentalization of the Magnolia field, as observed in studies based on reservoir pressure and fluid phase (Weissenburger & Borbas, 2004; McCarthy et al. , 2005, 2006).…”

“…Seismic and borehole data indicate that the reservoir is heterogeneous and includes thick, blocky sandy turbidites, mass transport deposits and thinner bedded CRCL-rich successions. Furthermore, fluid pressure, phase and compositional data indicate that the reservoir is highly segmented and compartmentalized (Weissenburger & Borbas, 2004;McCarthy et al, 2005McCarthy et al, , 2006 due to syn-depositional and postdepositional faulting due to allochthonous salt movement. The only cored well in the field, located near the salt-cored sill of the mini-basin Consists of one sedimentation unit of increasing-climb-angle CRCL that records the increasing suspension fallout rate of a waning, collapsing flow.…”

“…Furthermore, CRCL are commonly deposited in off-axis depositional environments where significant amounts of mud also accumulate between events. These factors, combined with fault-related heterogeneity, have led to the intense compartmentalization of the Magnolia field, as observed in studies based on reservoir pressure and fluid phase (Weissenburger & Borbas, 2004;McCarthy et al, 2005McCarthy et al, , 2006. Consequently, it can be expected that CRCLrich reservoirs will exhibit decreased vertical and horizontal permeability and poor well communication compared with reservoirs composed of massive, coarser grained facies.…”