Conoco Inc.

Conocophillips Company

David W Bell

Alan Royce Huffman

Shein S Wang

Richard Wayne Lahann

Ernest C Onyia

Jerry Lee Kisabeth

Gregory Joseph Jorgensen

John B Sinton

Robert Lankston

Vernon D Cox

Gregory L Loumos

Stephen J Hill

A method of determination of fluid pressures in a subsurface region of the earth uses seismic velocities and calibrations relating the seismic velocities to the effective stress on the subsurface sediments. The seismic velocities may be keyed to defined seismic horizons and may be obtained from many methods, including velocity spectra, post-stack inversion, pre-stack inversion, VSP or tomography. Overburden stresses may be obtained from density logs, relations between density and velocity, or from inversion of potential fields data. The seismic data may be P-P, P-S, or S-S data. The calibrations may be predetermined or may be derived from well information including well logs and well pressure measurements. The calibrations may also include the effect of unloading. The determined pressures may be used in the analysis of fluid flow in reservoirs, basin and prospect modeling and in fault integrity analysis.

Method and process for prediction of subsurface fluid and rock pressures in the earth

A method for modeling geological structures includes obtaining seismic data and using these data to derive an initial density model. Potential fields data is used to update the initial geophysical model by an inversion process using vector or tensor components of gravity and/or magnetic data. In regions having an anomalous density zone, the initial model includes a topographic or bathymetric surface and a 2D or 3D density model including the top of any zones of anomalous density. Potential fields data is then used to derive the lower boundary of the anomalous density zones by using an inversion process. The final density model from the inversion may be further refined using the seismic data in conjunction with the model obtained by inversion of the potential fields data. The model data are integrated two or three dimensions to determine an overburden stress for the subsurface that includes a proper treatment of the anomalous density zone. In an optional process, the seismic data can be processed in depth or time using the density model from the inversion to improve the quality of the velocity information adjacent to and beneath the anomalous bodies.

Method for gravity and magnetic data inversion using vector and tensor data with seismic imaging and geopressure prediction for oil, gas and mineral exploration and production

A method of determination of fluid pressures in a subsurface region of the earth uses seismic velocities and calibrations relating the seismic velocities to the effective stress on the subsurface sediments. The seismic velocities may be keyed to defined seismic horizons and may be obtained from many methods, including velocity spectra, post-stack inversion, pre-stack inversion, VSP or tomography. Overburden stresses may be obtained from density logs, relations between density and velocity, or front inversion of potential fields data. The seismic data may be P-P, P-S, or S-S data. The calibrations may be predetermined or may be derived from well information including well logs and well pressure measurements. The calibrations may also include the effect of unloading. The determined pressures may be used in the analysis of fluid flow in reservoirs, basin and prospect modeling and in fault integrity analysis.

A method for modeling geological structures beneath anomalous density zones includes receiving seismic data and using this data to derive the top of a geologic model. Non-seismic data, such as gravity or magnetic data are used to derive the lower boundary of the geologic model in an inversion process. In one embodiment, the predicted parameters are combined with seismic data to obtain a depth image and to derive a velocity model in delineating formations of interest. In another embodiment, the processed seismic data is used to further constrain the inversion of the non-seismic data. Another novel aspect of the invention is the filtering of the non-seismic data during the inversion process in a manner that is consistent with Laplace's equation.

Method for integrating gravity and magnetic inversion data with model based seismic data for oil, gas and mineral exploration and production

A hybrid velocity model is used to image the subsalt reflector. A method for imaging subsalt reflectors includes receiving seismic data and depth migrating the raw data. Generated seismic P-waves are assigned a first P-wave velocity for travel outside a salt wedge. Prior to entering the salt wedge, the wave is treated as a compressional wave. Upon entering the salt wedge, the P-wave is treated as a converted S-wave and a corresponding S-wave velocity is assigned to the converted wave. When the converted S-wave exits the salt wedge, it is again converted, this time back to a P-wave. As this wave travels through the subsalt layer to a reflector interface, it is assigned a P-wave velocity. Thus, a velocity model which includes both P-wave and S-wave velocities is used to image reflectors below salt wedges.

Method for using P-S converted waves as a subsalt imaging tool

A method for generating a three dimensional velocity model from a grid of two dimensional lines is presented. Each of the two dimensional lines is common offset depth migrated and the migrated common offset sections are sorted into common image point (CIP) gathers. The proposed method examines all the common image point gathers from all the two dimensional lines and extracts out of plane three dimensional information. An initial three dimensional model is constructed from the two dimensional depth sections by mapping the depth images of several reflectors from each two dimensional line. Ray tracing through this initial three dimensional model, the out of plane three dimensional information is used to compute a set of corrections to the boundaries in the three dimensional model. The three dimensional model boundaries are then iterated until all mismatches are minimized. The final model can be used for a final three dimensional depth migration, or as a three dimensional interpretation in agreement with all the two dimensional lines.

Method of extracting three dimensional information from a grid of two

The invention relates to a method for locating correct near vertical boundary or fault positions in a velocity model using common reflection point (CRP) gathers. Conventional migration velocity analysis examines the migrated image for hints to correct the velocity model. Vertical boundaries such as faults or salt flanks must be accurately determined to produce reliable images of deeper reflectors. Previous methods have placed faults by trial and error, since a depth image of a nearly vertical boundary is difficult to produce. The present method examines the sensitivity of CRP gathers to abrupt lateral changes across a nearly vertical fault to determine the location and the dip of a nearly vertical fault from a series of CRP gathers.

Method of accurate fault location using common reflection point gathers

A method for determining the location of steeply dipping subsurfaces includes acquiring seismic reflection data, identifying select data which has characteristics indicating that the acoustic pulses which it represents have been reflected from a substantially horizontal interface and a steeply dipping interface, analyzing the select data to locate the steeply dipping interface and displaying the analyzed data.

Seismic imaging of steeply dipping geologic interfaces

A process for separating upgoing and downgoing seismic wave events in a vertical seismic profile, and particularly for vertical seismic profiles wherein the seismic energy source is offset from the borehole in which seismic detectors are located in vertical spaced array. The process operates on two detector signals at a time (as S.sub.1 and S.sub.2) and is based on the concept that waves traveling in opposite directions have spatial derivatives of opposite sign. The derivative is approximated by the difference of the two signals which is time integrated to recover the phase. The resulting integrated difference signal I is then amplitude scale corrected and combined by addition or substraction with a signal S.sub.0 representing the sum of the two detector signals to form a succession of filtered signals which, when recorded in alignment in order of detector depths to form a vertical seismic profile preserves either the upgoing or the downgoing seismic events.

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Ponca City, OK, United States of America

David W Bell