Maggie Smith

Seismic reservoir characterization of a U.S. Midcontinent fluvial system using rock physics, poststack seismic attributes, and neural networks

In a U.S. Midcontinent gas field, a channel feature contained shale and reservoir sands ranging in porosity from 6% to 20%. Well logs, core data, and 3D seismic data were combined in a reservoir characterization study to map the lithology and variability of porosity within the target sand. The project was conducted in two phases—a qualitative, uncalibrated seismic attribute study and a detailed well-log-calibrated reservoir characterization.

The Use of Fluid Substitution Modeling For Correction of Oil Based Mud Filtrate Invasion In Sandstone Reservoirs

Summary Mud filtrate invasion can occur in many types of permeable hydrocarbon bearing formations. It often causes sonic logs to be too fast and density logs to be too high because these logs are sampling mostly water saturated rock. Uncorrected, it can cause substantial errors in well ties to seismic. The problem can be easily detected with multiple depth resistivity logs and then can be corrected using careful application of Biot-Gassmann fluid substitution.

Seismic reservoir characterization of a mid-continent fluvial system using rock physics, poststack seismic attributes and neural networks; a case history

Rock Solid Images 2600 S. Gessner, Suite 650 Houston TX 77063 713.783.5593, Fax 713.783.5594 www.rocksolidimages.com Seismic reservoir characterization of a mid-continent fluvial system using rock physics, poststack seismic attributes and neural networks; a case history Joel D. Walls*, M. Turhan Taner, Gareth Taylor, Maggie Smith, Matthew Carr, Naum Derzhi Rock Solid Images, Houston, TX Jock Drummond, Donn McGuire, Stan Morris, John Bregar, James Lakings Anadarko Petroleum Corporation

Seismic Attribute Analysis In Hydrothermal Dolomite, Devonian Slave Point Formation, Northeast British Columbia, Canada

Recent advances in visualization technology and seismic attribute analysis are beginning to revolutionize the landscape of 3-D seismic interpretation. This presentation focuses on the interpretive use of post-stack seismic attributes for seismic reservoir characterization. Multiple seismic attributes facilitate structural interpretation and recognition of seismic stratigraphy, but as importantly, they may offer clues to lithology typing and estimation of fluid content from seismic data. Potential benefits include reduction of stratigraphic and structural drilling risks, seismic reservoir characterization in exploration settings, and value increase of new and vintage 3D seismic data. Immediate improvements in drilling risk reduction can be obtained by using multiple seismic attributes. This enhancement occurs because each seismic attribute computation resembles a non-linear filter that decomposes reflection data into its constituents, and, as a consequence, use of multiple seismic attributes restores much of the discriminating information retained in the originally recorded wavefield (Barnes, 2001; Taner, 2001). Thus, each seismic attribute, for instance, amplitude, inadvertently contains only a subset of the total information recorded, since a single seismic attribute represents only one numerical property of a propagating seismic wavefield. In this presentation, we advocate the use of geometric attributes in conjunction with relative acoustic impedance and frequency-derived seismic attributes. In the past, use of geometric attributes was mostly limited to edge detection, where edges in the seismic data commonly represent faults or stratigraphic terminations (seismic facies changes). In this Devonian Slave Point Formation case study, we use post-stack seismic attributes to

Lithology substitution in fluvial sand

Dichotomy in geophysical remote sensing is both relative and absolute: while the seismic reflection relates to the impedance contrast, the reservoir properties, such as porosity, relate to the absolute value of the impedance. One way of interpreting the relative in terms of the absolute is to perturb the absolute and calculate the corresponding relative. To accomplish this task in geophysics, the velocity and density curves from an existing prototype well are perturbed according to a likely situation at a different location. A new pseudowell thus created is used to generate synthetic full-waveform seismograms which are then compared to real data at the location, with the expectation that the similarity in the seismic response reflects the similarity in the reservoir properties.

From qualitative to quantitative interpretation: An interpreter’s guide to fluid prediction in Pliocene to Turonian deepwater turbidites from West Africa to Asia Pacific

AbstractTo mitigate exploration risk in deepwater settings, subsurface analysis increasingly has to rely on integration of qualitative with quantitative techniques. To predict pay in turbidite sandstones, proven statistical and analytical methods can routinely be run on well and seismic inversion data. However, quantitative interpretation (QI) should begin with a responsible audit of available well logs and seismic data, succeeded by data conditioning, proceeding with quality control, and placing elastic attribute responses within their geologic context. To address these issues, we evaluate geologic controls on porosity change as manifested by overpressure and compaction on calibration and analysis of elastic attributes. Following calibration of seismic inversion data, we provide tutorial-style interpretations of deepwater clastic reservoirs from the Gulf of Guinea, West Africa, to the Sabah trough, Borneo. Case study examples offer interpreters the potential to use workflows surrounding data mining in ex...

Seismic detection of juvenile reservoir character under leaky fluid cushions (including subsalt)

Fluid layers (such as salt) which are largely incompressible and which support overburden in the subsurface most often represent difficult drilling owing both to their ability to flow as well as usually exhibiting higher than what might be considered normal temperatures and pressures. The incentive for penetrating such formations are typically high quality reservoirs which lie below them. We now begin to understand that if the fluid layer can move laterally or “leak” (i.e. flow, deform or even dewater for the case of a shale section) the effective result shields deeper units from some measure of the overburden induced compaction processes. Of course we know from the higher conductivity of the fluid layer and temperature profile that thermal maturation of source rocks below this fluid zone would be retarded as well. Hence we can anticipate that target reservoirs under “leaky” fluid layers or “cushions” will exhibit juvenile reservoir character (less compacted or altered) relative to their actual geologic age and depth. While the physics of such phenomena and its modeling and representation constitute a fascinating technical endeavor, the most immediate piece of practical information we might wish to have would be a measure however crude of the retardation of reservoir “state” relative to anticipated properties. Of course we wish to have such information in advance of drilling as well. We know quite clearly from the Gulf of Mexico subsalt penetrations that the differences may be great. Yet a direct calculation would involve the particular fluid (salt or shale for example), rates of leakage, absolute depths, temperatures and the chemical constitution and depositional styles of the sediments as well as other factors many unknown. This daunting number of unknowns leads us to suggest that our best current hope for a successful approach to determining the information we seek rests with measurement of relative sand/shale reflectivity state (Figures 1 and 2). We may use both well logs as well as seismic data in attempts to develop such relations. Our knowledge generally concerning this phenomenon and indeed the proposed method of measurement is quite primitive at this time. Nevertheless, we feel it important to document a potentially promising avenue having likely practical value in order to address the problem during that time in which our knowledge base expands. Emphasis here will focus on this measurement procedure rather than on the physics and mechanics of the flow and deformation processes involved. Clearly these are worthy of study as well, but in our view at