Abstract: Novel maleimide copolymers have at least two monomeric units, a maleimide unit and a vinyl unit having a pendant group, the pendant group having two to twenty-one carbon atoms, at least one nitrogen atom and at least one oxygen atom. The copolymer has an average molecular weight between about 1,000 and about 6,000,000. Preferred maleimide copolymers include acrylamide/maleimide copolymers, N-vinyl amide/maleimide copolymers, vinyl lactam/maleimide copolymers, alkenyl cyclic imino ether/maleimide copolymers, and acryloylamide/maleimide copolymers. The substantially water soluble maleimide copolymers are useful for inhibiting the formation of clathrate hydrates in a fluid having hydrate-forming constituents by reducing the rate of nucleation, growth, and/or agglomeration of gas hydrate crystals in a petroleum fluid stream, thereby inhibiting the formation of a hydrate blockage in the pipe conveying the petroleum fluid stream.

Abstract: A method for producing seismic images from seismic data obtained from two different datums. Traveltimes between the two datums are determined from either measurements or an assumed velocity field. An extrapolation of the data to simulated source and receiver locations is carried out using any form of the wave equation which does not require velocity field information. After extrapolation, the data at the simulated source and receiver locations is processed using standard seismic imaging techniques. The method can be applied to simulate borehole, crosshole, or multi-borehole seismic data.

Abstract: The invention disclosed herein is a method for producing oil from a reservoir after predetermining its residual oil saturation, S.sub.orm. Such a method would displace a hydrocarbon fluid in a subterranean formation using a substantially non-aqueous displacement fluid after a waterflood. The non-aqueous displacement fluid can be introduced as a single bank, in alternating sequence with water, or by other means. The method predetermines S.sub.orm using the difference in the solubility parameters between the hydrocarbon liquid in the formation and the displacement fluid to be used for displacing the hydrocarbon fluid. The solubility parameter of the hydrocarbon liquid can be determined by a variety methods including, but not limited to, (1) using the hydrocarbon liquid's energy of vaporization, .DELTA.E.sub.

Abstract: A neutron logging tool is used to obtain information about fluids within a wellbore. The well is shut in and a neutron log count rate (M.sub.gas) is obtained in a portion of the wellbore containing primarily gaseous fluid and a neutron log count rate (M.sub.liquid) is obtained in a portion of the wellbore containing primarily liquid fluid. Then fluid flow is reestablished in the well and a neutron log count rate (M.sub.mix) is obtained over a logging interval of interest. Previously obtained calibration data relates (M.sub.gas), (M.sub.liquid), and (M.sub.mix) to relative quantities of gaseous fluid and liquid fluid within the wellbore.

Abstract: The invention relates to a multivariate method of inverting paleothermometer and age indicator data to derive the temperature history of rocks. The method uses kinetic models of geologic material transformations and a simple but flexible representation of bed temperature history to invert the paleothermometer data. The method inverts the data by employing a genetic algorithm computation and kinetic model S. The result is a family of temperature histories which more accurately and more completely characterize temperature histories consistent with the rock samples than is possible by prior art methods.

Abstract: A method of migrating seismic data using offset checkshot survey measurements. The offset checkshot survey measurements involve raypaths similar to the migration raypaths for the seismic data, and are used to determine direct arrival traveltimes to receivers in a borehole. Embodiments of the invention provide for direct use of the traveltimes in migration, or indirect use of the traveltimes in migration via construction of a migration velocity model. The velocity model embodiments further provide for either traveltime error correction via use of interpolated error functions or construction of migration error tables. The invention can be employed for time, depth or Kirchhoff migration, in either two or three dimension, and in either prestack or poststack applications.

Abstract: A method of geophysical prospecting using seismic trace attribute analysis for formation characterization. More particularly, a method for selection of seismic traces which most accurately represent the subsurface formation in the area of a seismic survey is disclosed. In one embodiment, inflection-point interval analysis is used to account for effects of local surfaces.

Abstract: A process for generating a surface slice for use in understanding or comprehending the internal structure of a multi-dimensional data volume and specifically a three-dimensional seismic data volume. The surface slice is a local N-1 dimensional representation of the internal structure of N dimensional data, where N represents the original dimension of the data volume. Information from the Nth-dimension is preserved in the N-1 dimensional surface slices. An arbitrary surface intersecting surfaces through the data volume is selected. A variant, an identifiable attribute of data which forms the surfaces of finite extent throughout the data volume, is also selected and isolated to identify the surface. Variants can include, but are not limited to, peaks, troughs, local peaks, local troughs, plus-to-minus zero crossings, and minus-to-plus zero crossings.

Abstract: A device for positioning two threaded pipes being threaded together within a target range of relative axial positions, which device generally includes a sensor base, and a calibrating device for positioning the sensor base a calibrated distance from the end of one of the pipes. The device further includes a sensor head extending from the sensor base, for abutting the end of the second threaded pipe during the threading of the pipes together, to indicate a relative axial position of the pipes. The device even further includes a signal generator that generates a signal once the sensor head indicates the relative axial position of the pipes are within the target range of relative axial positions.

Abstract: A method of processing geophysical data on a parallel processor. The method involves decomposition of an analysis cube into depth slices, a second decomposition of a data acquisition cube into traveltime slices, and determination of a variably dimensioned analysis aperture. Precomputed traveltimes are stored in packed format to minimize storage volume and data bandwidths. The method relies on staged access of traveltime fields from high speed mass storage to disk storage and via input/output processors to analysis processor memory. The input/output processors monitor analysis processor memory to optimize the direct scatter download of traveltime fields to the analysis processors. The seismic trace data download is also staged, preferably from tape storage to disk storage to processor memory. A control processor preprocesses the trace data while downloading the trace data from disk storage to processor memory.

Abstract: Disclosed is a method for creating a gain function for seismic data and to processing methods for utilizing such a gain function. The method of creating the gain function generally includes representing the seismic data as a plot of the logarithm of amplitude versus time. Various order polynomial functions are subsequently fitted to the plotted seismic data. The best fitting polynomial is then selected from these various order polynomials, the inverse of which is the gain function. This gain function can be utilized in a seismic processing method.

Abstract: Disclosed is a method for efficiently and accurately determining subsurface velocities for use in migration of seismic data. The method calls for restricting the number of traces considered to those lying upon that portion of the Kirchhoff summation curve wherein the integrand for Kirchhoff migration is smooth. In the preferred embodiment, only a random sample of traces within this aperture are used in the calculations. Improvements in efficiency on the order of a factor of 1000 can be realized with the preferred embodiment.

Abstract: Disclosed is a method of datuming seismic trace data from a first horizon to a lower second subsurface horizon, both located above a target horizon. A seismic source and receiver are positioned along the first horizon and each assigned a coordinate representing a position along the first horizon. The seismic trace data includes both header information and seismic data. The header information includes the coordinates assigned to the source and receiver. The seismic data is a record of reflection amplitude versus travel time of a seismic signal traveling from the source, downward through and intersecting the second horizon at a downward intersection point, reflecting upward from the target horizon, upward through and intersecting the second horizon at an upward intersection point, and upward to the receiver. The method generally includes determining for both the downward upward intersection points, coordinates along the second horizon corresponding to positions along the second horizon.

Abstract: A water-based well completion and workover fluid is disclosed which has improved rheological and filtration control properties at temperatures up to about 450.degree. F. The composition comprises a saturated brine solution, a sized-salt that is insoluble in the saturated brine solution, and a water-soluble filtration additive comprising a polymer produced from at least two monomers selected from the group consisting of 2-acrylamido-2-methylpropanesulfonate, acrylamide, and 2-vinylpyrrolidone.

Abstract: A method for inhibiting the formation of clathrate hydrates in a fluid having hydrate forming constituents is disclosed. More specifically, the method can be used in treating a petroleum fluid stream such as natural gas conveyed in a pipe to inhibit the formation of a hydrate restriction in the pipe. The hydrate inhibitors used for practicing the method are substantially water soluble polymers formed from a N-substituted acrylamide having two nitrogen substituent groups, R.sub.1 and R.sub.2, where R.sub.1 is a hydrocarbon group having from one to ten carbon atoms and zero to four heteroatoms selected from the group consisting of nitrogen, oxygen, sulfur, and combinations thereof, and R.sub.2 is a hydrogen atom or a hydrocarbon group having from one to ten carbon atoms selected from the group consisting of carbon, nitrogen, oxygen, and sulfur; alternatively, R.sub.1 and R.sub.

Abstract: A method for producing seismic images from seismic data obtained from two different datums. Traveltimes between the two datums are determined from either measurements or an assumed velocity field. An extrapolation of the data to simulated source and receiver locations is carried out using any form of the wave equation which does not require velocity field information. After extrapolation, the data at the simulated source and receiver locations is processed using standard seismic imaging techniques. The method can be applied to simulate borehole, crosshole, or multi-borehole seismic data.

Abstract: A method for three dimensional migration of a two dimensional grid of seismic data. The method involves computation of three dimensional time-dip functions at the intersections of lines in the grid. Inverse raytracing is used to correctly position the reflection events in the three dimensional volume encompassed by the grid. Migration of the seismic data is performed onto image surfaces defined from the correctly positioned reflection events.

Abstract: A seal assembly for use in completion and production operations of a subterranean hydrocarbon well for sealing the annular space between the production casing and tubing, which assembly generally includes primary seal members having a circular, oval or elliptical shaped cross-sections, and secondary seal members having convex sections for abutting the primary seal members. The assembly further includes retainers on the tubing which define the seal bore into which the seal members are positioned, and a polished surface on the casing for allowing movement of the seal members against the casing.

Abstract: A method for inhibiting the formation of clathrate hydrates in a fluid having hydrate forming constituents is disclosed. More specifically, the method can be used in treating a petroleum fluid stream such as natural gas conveyed in a pipe to inhibit the formation of a hydrate restriction in the pipe. The hydrate inhibitors used for practicing the method are substantially water soluble polymers formed from a cyclic imino ether. Such polymers may be ring closed cyclic imino ether ("CIE") polymers, ring opened CIE polymers, or combinations thereof. Some examples of ring opened CIE polymers include various N-acyl polyalkyleneimines produced by cationic polymerization, such as N-acyl substituted polyethyleneimine, N-acyl substituted polypropyleneimine, N-acyl substituted polybutyleneimine, N-acyl substituted polypentyleneimine and copolymers thereof.

Abstract: A method for removing non-geologic amplitude variations from seismic data. The method is based on the premise that lateral amplitude variations with spatial wavelengths shorter than the width of the Fresnel zone, a known wave propagation effect, for the target cannot be caused by changes in the reflectivity of the target and must, therefore, be due to non-geologic causes. The method permits these non-geologic amplitude effects to be identified and removed from the seismic data. The method may be implemented either manually or automatically by a computer.