181 results about "Density logging" patented technology

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 for evaluating cement quality in a cased well. A density log of the well is obtained using, for example, a GammaRay sources and detectors (51). The detector count rates are inverted to provide initial estimates of cement density and thickness (53). Acoustic waveform data are obtained from the well using an acoustic logging tool (52). The acoustic data are inverted (54-56), using the initial estimates of cement density and thickness obtained from the density logs, and an updated density log is inferred. Cement images are obtained from the updated density log, and cement bond quality can be estimated (57).

The invention discloses a method of estimating permeability of a low porosity and permeability reservoir and belongs to the field of petroleum geological prospecting. The method comprises: calculating limestone porosity according to acoustic, neutron and density logging curve; calculating first shale content index according natural potential logging curve; calculating second shale content index according to natural gamma logging curve; calculating lithological index of reservoir rock according to the limestone porosity calculated according to the acoustic, neutron and density logging curve; calculating particle diameter of the reservoir rock according to the first shale content index, the second shale content index and the reservoir lithological index; calculating cementation index according to statistical fitting relation between resistivity and the porosity; estimating permeability according to the particle diameter d of the reservoir rock and the cementation index m of the reservoir. High-precision calculation results for the permeability of the low porosity and permeability reservoir are achieved by using the calculation relation between the various logging curves and the permeability of the invention, and a powerful tool is provided for evaluating the permeability of a reservoir with low porosity and permeability, complex lithology and complex porous structure.

It relates to a method of predicting the collapse and crack pressure underground with the drilling head. Recording the earthquake status of a well to be drilled and several other adjacent drills that have already been drilled, getting the earthquake record of the well to be drill and already drilled through weighting, through sound wave echoing difference and density measuring for the already drilled wells to get the log data of different strata, a hierarchical model can be established to predict the sound wave speed and wave resistance of each strata based on the earthquake record. Through the log curve predicted of the strata of the well to be drilled, the collapse and crack pressure of the strata can be predicted combined with the interpretative model of the well wall stability mechanics logging. It can effectively prevent the collapse of the well wall and accidents occurrence underground.

The invention discloses a borehole stability evaluation method for a highly-deviated well. The borehole stability evaluation method includes steps of adopting interval transit time and density logging information to obtain formation pressure Pp, and determining the magnitude and direction of ground stress and formation rock strength parameters; converting the obtained ground stress into borehole stress of deviated well coordinates; determining the criterion of borehole instability judgment of the highly-deviated well; establishing a variation rule between borehole instability and deviation and azimuth angles thereof, and formulating borehole stability countermeasures of the highly-deviated well. In the borehole stability evaluation method, a set of complete and assorted mechanical evaluation methods combined with geology, well drilling, logging, core, laboratory tests and mechanics analysis methods takes shape, mechanical mechanism of borehole stability of the highly-deviated well can be evaluated, so that reliable basis is provided for determination of platform displacement optimization, borehole track optimization and a safe drilling fluid density window determination of the highly-deviated well.

The invention relates to a seismic horizon calibration method utilizing a vertical seismic profiling (VSP) and well-logging combination. The seismic horizon calibration method comprises the following steps: measuring and obtaining a longitudinal wave time-depth relationship and a corridor stacking profile according to zero offset data, performing well logging and obtaining acoustic well logging and density well logging data, calculating an acoustic wave time-depth relationship and a VSP time-depth relationship to get time difference, correcting an acoustic wave curve, obtaining a synthetic record through corrected well-logging curve and seismic wavelet convolution, making a horizon calibration chart after the time shift quantity of a VSP corridor and the correct polarity are determined and performing horizon calibration on a ground seismic profile according to known drilling geological stratification. According to the seismic horizon calibration method, the acoustic well logging error and the frequency dispersion effect are eliminated, the synthetic record making precision is improved, human factors in the calibration are reduced, and the calibration accuracy is improved.

The invention relates to an inversion method of stratum shear wave velocity radial sections. The inversion method includes: performing acoustic logging while drilling and while drilling stratum density and well diameter logging in a depth interval, and obtaining while drilling monopole and quadrupole array acoustic full wave train data, a while drilling stratum density logging curve and a while drilling well diameter logging curve; obtaining stratum longitudinal wave velocity and shear wave velocity at the position of processing depth through calculation, and extracting phase velocity frequency dispersion data of while drilling quadrupole wave; calculating a theoretical while drilling quadrupole wave frequency dispersion curve at the position of the processing depth; constructing an inversion objective function in a combined mode; outputting equivalent alteration velocity and thickness; calculating continuously variable stratum shear wave velocity radial sections; and repeating the steps until processing of the whole depth interval is finished, and obtaining the stratum shear wave velocity radial sections changing continuously along with logging depth. The inversion method of stratum shear wave velocity radial sections has the advantages of obtaining changes of mechanics/acoustic parameters nearby a well in real time, solving the problem of ununiqueness of inversion, and improving reliability of inversion results.

A pulsed neutron source is used in a density logging tool with three or more detectors. This enables compensation for source variations and provides redundant measurements that are used to make borehole corrections and/or corrections for casing.

An acoustic transducer on a downhole tool sends an acoustic wave through a sensor plate. The signal is reflected by the borehole wall back towards the transducer. The received signal is responsive to the formation impedance.

The invention discloses a method for recognizing engineering sweet spots in a shale stratum. The method includes the following steps that the maximum horizontal effective stress value of the shale stratum is determined according to sound wave and density logging information and dipole sound wave logging information; the pore structure index of the shale stratum is obtained according to imaging logging information and physical parameters; the brittle mineral content in the shale stratum is determined based on element logging information and is used for determining the brittleness index of the shale stratum; and according to the maximum horizontal effective stress value, the pore structure index and the brittleness index of the shale stratum, the engineering sweet spot coefficient of the shale stratum is determined through a radar map analyzing method, and the engineering sweet spot coefficient is used for recognizing the engineering sweet spots in the shale stratum. By analyzing the engineering sweet spot coefficient of the shale stratum, it is determined that the brittleness index, the maximum horizontal effective stress value and the pore structure index are the main parameters of the engineering sweet spots in the shale stratum, and the engineering sweet spots in the shale stratum can be accurately recognized according to the existing logging information.

The invention discloses a manufacturing method and a device for synthesizing earthquake record. The manufacture method comprises steps of obtaining earthquake data comprising time-depth relation data and corridor stack profile data, utilizing the time-depth relation data to perform correction processing on acoustic logging data, obtaining corrected acoustic logging data and depth correction data, utilizing depth-correction data to perform correction processing on density logging data to obtain corrected density logging data, obtaining a reflection coefficient sequence according to the calculation of the corrected acoustic logging data and corrected density logging data, utilizing time-depth relation data to perform time-depth conversion on the reflection coefficient sequence to obtain time-domain reflection coefficient sequence, determining a dominant frequency curve according to the corridor stack profile data, generating a ricker wavelet set, and performing convolution calculation on the ricker wavelet set and the time-domain reflection coefficient sequence to obtain synthesized earthquake record. The invention can obtain the synthetic earthquake record according with the reality.

Methods for density logging utilizes gamma-rays above a pair-production threshold so as to determine lithology information of formations whereby to correct a measured density data.

The invention relates to the rib-expansible density logging while drilling apparatus for use in the petroleum drilling industry. A density detector pup joint and a gamma radioactive source are sealed and arranged on a drill collar. An expandable rib is arranged on the surface of the drill collar at position of a groove, and the groove and the density detector pup joint are arranged at an interval of about 120 degrees in a circumferential direction. The expandable rib relies on a piston assembly to extend outward under the action of pressure drop (difference between inner pressure and outer pressure) generated due to instruments such as a drill bit (and a motor) arranged at the lower part of the apparatus and presses the detector pup joint against a well wall on a corresponding side by using counterforce of the well wall to realize density measurement by the well wall. And when a pump stops, the expandable rib retracts under the action of a return spring. The rib-expansible density logging while drilling apparatus is applicable to various wells, ensures measurement by the well wall, overcomes influence of slurry, mud cake or complex well structure on measurement precision, improves underground safety and is applicable to logging while drilling and geosteering drilling.

In connection with a downhole density logging method and tool, the gamma ray source and detectors are substantially non-shielded (that is, they are omni-directional). As a result the gamma ray emission produced by the ‘omni-directional’ source is non-collimated and the back-scattered gamma rays counted by the omni-directional detectors are also non-collimated. Testing has shown that density logging through well casing is viable using this system.

The invention provides a method for predicting gas content of shale by using seismic data and belongs to the petroleum and natural gas exploration field. The method includes the following steps that: (1) geological, logging and seismic data are prepared; (2) a density logging curve-based gas content calculation model, that is VGAS=f(DEN) (1), is established through using high correlation between a density logging curve and shale gas content data, wherein VGAS is gas content, m<3>/t, DEN is a density logging curve, g/cm<3>, and f is a function relational expression between gas content and density; (3) post stack multi-attribute inversion is carried out, so that density curve data required by the gas content calculation model can be obtained; and (4) gas content prediction is carried out: the density curve data obtained in the step (3) are introduced into the formula (1), so that the gas content of the shale can be obtained.

The invention relates to a logging information-based lithotype determining method, which is characterized by comprising the steps of respectively collecting the parameter data of a coring well and an unknown well; selecting a compensated density logging curve, a compensated sound wave time difference logging curve, a compensated neutron logging curve and a borehole diameter logging curve, which are sensitive to lithotypes as basic parameters, counting the electrical parameter distribution intervals of different lithotypes by the true depth determination of core of the coring well, establishing a coal and rock logging classifying standard and a coal and rock identification plate, and determining the lithotype of the unknown well by adopting a plate method or a gray correlation statistical method. The logging information-based lithotype determining method has the advantages of solving the difficult problem that the lithotype can be determined by only rock coring, offsetting the defect that the cost for lithotype determining through naked eye observation is high, and realizing the fast and continuous identification on the lithotypes under the condition that a coal-bed gas well is not subjected to rock coring.

Measurements made with porosity and density logging tools in a gas reservoir may differ due to invasion effects. The effects are particularly large on measurement-while-drilling applications where invasion is minimal. Using a Monte-Carlo method, a relationship is established between true formation porosity and porosity estimates from density and porosity tools. This relationship is used on real data to get an improved estimate of formation porosity and of gas saturation.

The invention discloses a method of conducting seismic frequency extension by utilizing acoustic logging, which comprises the following steps: making a wide-band synthetic seismic record through a reflection coefficient sequence obtained by acoustic logging date and density logging data, and selected high frequency seismic wavelet; comparing the synthetic wide-band seismic record with cross-well seismic traces to obtain a law of longitudinal high-frequency signal loss caused by a low-pass stratum filter; meanwhile, utilizing the contrastive analysis of a near-well seismic record and any seismic trace on a cross-well section to obtain the filter effect of lateral variation of the stratum; and by studying the amplitude spectrum properties of the filter, summarizing the properties of a longitudinal filter and a transversal filter on a seismic stack section, designing a frequency extension series inverse filter with longitudinal frequency loss and transversal frequency change, and using the frequency extension series inverse filter on a cross-well seismic stack section to achieve the purposes of extending the bandwidth and improving a stacked reflective seismic section resolution, and provide more detailed and reliable seismic information for the elaboration and the dynamic monitoring of oil and gas reservoir.

The invention discloses a method for judging a tight sandstone gas reservoir based on the compressibility factor of the pore fluid. According to the technical scheme of the invention, the time difference of longitudinal waves and the time difference of transverse waves are provided based on the array sonic logging information. Meanwhile, the formation density of the density logging information is adopted as the input information to calculate a formation bulk modulus, so that the compressibility factor of reservoir rocks is derived. In combination with a formation bulk model, the compressibility factor of the pore fluid can be further derived. Finally, based on the compressibility factor of the pore fluid, whether the fluid is a tight sandstone gas reservoir or not can be judged. The acoustic information is deeply excavated in the method, and the difference between the compressibility factor of reservoir rocks and the compressibility factor of the pore fluid is utilized for the judgment of the fluid property. Therefore, the application range of the array sonic information for the judgment of the fluid property is broadened. Meanwhile, the judgment accuracy of the fluid property is improved.

The invention provides a glutenite lithological physical logging recognition method based on three-porosity curves. The glutenite lithological physical logging recognition method based on the three-porosity curves comprises the steps that 1, gamma, sound wave, density, neutron and electrical resistivity logging curve data is collected; 2, borehole environment correction is performed on gamma, sound wave and density logging curves; 3, sound wave, density and neutron three-porosity curves are displayed in a superposed mode; 4, a scale range of the sound wave, density and neutron three-porosity curves is determined; 5, glutenite and mudstone are comprehensively recognized in combination with cores, logging data and the sound wave, density and neutron curves; and 6, mineral constituents and afluid volume are comprehensively calculated. Through the glutenite lithological physical logging recognition method based on the three-porosity curves, glutenite and mudstone can be reasonably recognized, the mineral constituents and fluid properties can be calculated, and effective support is provided for logging interpretation, reservoir prediction, oil deposit evaluation, formulation of a development scheme and the like.