Key Laboratory of Earth Prospecting and Information Technology

Beijing, China

Key Laboratory of Earth Prospecting and Information Technology

Beijing, China

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Mao Z.-Q.,China University of Petroleum - Beijing | Mao Z.-Q.,Key Laboratory of Earth Prospecting and Information Technology | Xiao L.,China University of Geosciences | Xiao L.,Beijing University of Technology | And 4 more authors.
Applied Magnetic Resonance | Year: 2013

It has been a great challenge to determine permeability in tight gas sands due to the generally poor correlation between porosity and permeability. The Schlumberger Doll Research (SDR) and Timur-Coates permeability models, which have been derived for use with nuclear magnetic resonance (NMR) data, also lose their roles. In this study, based on the analysis of the mercury injection experiment data for 20 core plugs, which were drilled from tight gas sands in the Xujiahe Formation of central Sichuan basin, Southwest China, two empirical correlations between the pore structure index (√K/φ, defined by the square root of the ratio of rock permeability and porosity) and the R35 (the pore throat radius corresponding to 35.0 % of mercury injection saturation), the pore structure index and the Swanson parameter have been developed. To consecutively estimate permeability in field applications, based on the study of experimental NMR measurements for 36 core samples, two effective statistical models, which can be used to derive the Swanson parameter and R35 from the NMR T2 logarithmic mean value, have been established. These procedures carried out on the experimental data set can be extended to reservoir conditions to estimate consecutive formation permeability along the intervals with which NMR logs were acquired. The processing results of several field examples using the proposed technique show that the classification scale models are effective only in tight gas reservoirs, whereas the SDR and Timur-Coates models are inapplicable. The R35-based model is of significance in thin sands with high porosity and high permeability, but the predicted permeability curves in tight gas sands are slightly lower. In tight gas and thin sands, the Swanson parameter model is all credible. © 2012 Springer-Verlag.


Xiao L.,China University of Petroleum - Beijing | Xiao L.,Key Laboratory of Earth Prospecting and Information Technology | Mao Z.-Q.,China University of Petroleum - Beijing | Mao Z.-Q.,Key Laboratory of Earth Prospecting and Information Technology | And 2 more authors.
Journal of Petroleum Science and Engineering | Year: 2012

Permeability, irreducible water saturation and other information associated with the pore size, such as capillary pressure, are very important input parameters in tight gas reservoir evaluation. Fortunately, those parameters can be well estimated from field NMR logs, if the proper calibrations between NMR relaxation time and capillary pressure were established with measurements from core samples. In this study, a novel calibration technique, which is used for constructing capillary pressure curve from NMR logs by combining the classical SDR model with J function, is proposed and the corresponding model is established. Based on the laboratory measurements of 54 plug samples taken from the Upper Triassic sandstone formation (Xujiahe Formation) in Anlu district, Sichuan basin, Southwest China, the model parameters are calibrated. With the calibrations established and procedures proposed in this paper, the synthetic capillary pressure curves of reservoir can be constructed from field NMR spectrum. Also from those laboratory measurements, the parameter of Kφ (defined as the pore structure index) can be well related to the Swanson's parameter derived from capillary pressure curve. This correlation could then be used for estimating reservoir permeability from the synthetic capillary pressure curve. After formation is classified into three types by using the pore structure index, the pore throat radius cutoffs can be acquired to calculate irreducible water saturation from the pore throat radius distribution. The proposed techniques and procedures are applied in field logs and the estimated information and parameters are well verified by core and drill stem testing data. By combining with the information of reservoir pore structure, permeability and irreducible water saturation, potential low resistivity contrast gas bearing reservoirs can be identified from water layers. © 2012 Elsevier B.V.


Xiao L.,China University of Petroleum - Beijing | Xiao L.,Key Laboratory of Earth Prospecting and Information Technology | Mao Z.-Q.,China University of Petroleum - Beijing | Mao Z.-Q.,Key Laboratory of Earth Prospecting and Information Technology | Jin Y.,Petrochina
Applied Magnetic Resonance | Year: 2012

It is difficult to calculate irreducible water saturation (S wirr) from nuclear magnetic resonance (NMR) logs in tight gas sands due to the effect of diffusion relaxation on the NMR T 2 spectrum at present. By combining with classical Timur and Schlumberger-Doll Research (SDR) models, a novel model of calculating S wirr is derived. The advantage of this novel model is that S wirr can be calculated without a T 2 cutoff, and all input information can be acquired from NMR logs accurately. With the calibration of 36 core samples, which were drilled from Xujiahe Formation in Bao-jie region of Triassic, Sichuan basin, southwest China, the values of these statistic model parameters are defined. Field examples of tight gas sands show that the proposed model is reliable. The S wirr calculated with the proposed model match well with core analyzed results both in tight gas formations and water-saturated layers, the absolute error is in the range of ±4%. The calculated results by using 20.75 ms as the T 2 cutoff are accurate in water-saturated layers but are overestimated in gas-bearing intervals. Defining 33 ms as the T 2 cutoff is unusable both in gas-bearing and water layers. © 2011 Springer-Verlag.


Wang R.-J.,China University of Petroleum - Beijing | Wang R.-J.,Key Laboratory of Earth Prospecting and Information Technology | Qiao W.-X.,China University of Petroleum - Beijing | Qiao W.-X.,Key Laboratory of Earth Prospecting and Information Technology
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2014

A three dimensional time-domain finite difference (TDFD) approach is utilized to investigate the types, excitation amplitude and dispersive characteristics of borehole normal modes produced by cross-dipole sources with the existence of an eccentric drill collar. The results show that an eccentric tool excites wave field of multiple azimuthal orders, where we observe monopole and quadrupole modes besides the wanted dipole modes. We also observe the wave splitting phenomenon induced by the tool eccentricity, especially at relatively high frequency, for either the F2 mode of fast formations, or the flexural mode of slow formations. The orientations of fast and slow flexural waves induced by tool eccentricity are the directions parallel or perpendicular to the eccentric direction. The borehole refracted shear waves and the low frequency range of the F2 mode are almost not affected by the tool eccentricity, and can be utilized to accurately describe the shear slowness and the shear anisotropy. For the slow formation in this study, when l≤0.01 m, the influence of collar eccentricity on flexural amplitude and dispersion is relatively small, and the extracted fast and slow shear slowness from the flexural waves can be used to assess the formation elastic anisotropy.


Wang R.-J.,China University of Petroleum - Beijing | Wang R.-J.,Key Laboratory of Earth Prospecting and Information Technology | Qiao W.-X.,China University of Petroleum - Beijing | Qiao W.-X.,Key Laboratory of Earth Prospecting and Information Technology
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2014

We propose an asymmetric arcuate acoustic source to develop a three-dimension acoustic reflection LWD method, and deduce the mathematical description of the source in wavenumber-frequency domain. The acoustic field in the formation produced by the source is obtained by the real axis integration method, and the influences of the dimension and frequency of the source on the compressional wave field, SH wave field and SV wave field are investigated. The results indicate that only one main lobe is observed in the horizontal and vertical directivity of the compressional wave field produced by the arcuate source with specific size and frequency. The 3dB angular width of the main lope is narrow. Hence compressional wave field excited by the source is of high azimuthal resolution and suitable for the three-dimension acoustic reflection LWD. Two or more lobes exist in the directivity of SV field and SH field, and the radiant energy of the SV field at the direction perpendicular to the borehole axis is 0. Additionally, the reflected SH waves and SV waves may interfere with each other because of similar ray path and velocity. Therefore, it is difficult to image the geological structure in three-dimension by the SV field and SH field. The dimension and frequency of the source greatly impact the radiated wave field, and in consideration of the excitation efficiency and azimuthal resolution, for the borehole model described in this paper, the source with azimuthal width between 75° and 90°, and main frequency around 12 kHz is an appropriate choice.


Wang R.-J.,China University of Petroleum - Beijing | Wang R.-J.,Key Laboratory of Earth Prospecting and Information Technology | Qiao W.-X.,China University of Petroleum - Beijing | Qiao W.-X.,Key Laboratory of Earth Prospecting and Information Technology
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2015

The technique of reflected acoustic logging while drilling (RALWD), which is the development trend of the next-generation acoustic logging tool, affords to provide important data on rock formation structures and geological bodies in real-time and in three spatial dimensions (3D), which is helpful in guiding drill direction and optimizing well trajectory into the best position in the oil (gas) reservoir to achieve the desired effect of oil (gas) production or water injection. As the RALWD needs information in 3D, existing wireline single-well reflected acoustic methods, which have limited azimuth detection capability, cannot be adopted and new methodology is required. We propose a new asymmetric arcuate source/receiver, and investigate the feasibility of adopting this sources/receiver to perform RALWD in a fluid-filled borehole. The 3D acoustic reflection LWD with the asymmetric arcuate source/receiver is numerically simulated by adopting a 2.5D time-domain finite difference method (TDFD). The amplitude and phase of reflected signal versus azimuth angles and offsets is numerically investigated and analyzed. And based on the simulation results, we numerically study the feasibility to detect formation boundaries in horizontal wells by using these arcuate sources and receivers. Simulation results show that the arcuate source is able to transmit acoustic signals in desired direction with a radiation pattern including a main lobe of small angular width and side lobes of low degrees. The amplitude of the radiation wave field for this source is about 0.6 time that of conventional ring sources. These characteristics indicate that the proposed source is suitable for 3D RALWD. For the well model investigated in this paper, the reflected signals have an amplitude of 1/100 of borehole guided waves, and the amplitude of reflected compressional waves decreases with increasing offset, while that of reflected converted waves (P-SV, SV-P) increases first and then decreases as the offset increases, and the reflected SV strengthens with increasing offset. It suggests that it is possible to obtain better images by selecting waveforms with appropriate offset and suppressing non-target wave modes in the processing of field data. We also show results for a case of a horizontal well with the purpose to detect upper and lower rock formation boundaries by the arcuate sources and receivers. Results indicate that multi-signals, including reflected P and SV signals from the top and bottom boundary, are observed. The azimuths, which reach the maxima for reflected P-waves from top boundary and bottom boundary, are 0° and 180°, respectively, agreeing well with the input borehole model. The reflected P-waves are of desired azimuth resolution with a 3 dB of 48.6° and 49.4° for top and bottom boundaries, respectively. Note that, reflect signals from the top boundary do not exist in the waveforms of 180°, while those from the bottom boundary do not exist in the waveforms of 0°. These results suggest that it is possible to image top and bottom boundaries by processing the waveforms of the azimuths 0° and 180°, respectively, without interference to each other. The existence of a drill collar makes it possible for the source to omit acoustic signal along a desired azimuth direction, and the radiation pattern of the source has a main lobe with a narrow angle width as well as side lobes of low level, indicating that the proposed source is suitable for 3D RALWD. The case analysis for a horizontal well shows that the reflected compressional waves are of desirable resolution, and thus they can be utilized to obtain the azimuth of the reflector outside of the borehole. ©, 2015, Science Press. All right reserved.


Lu Q.,University of Science and Technology of China | Lu Q.,Key Laboratory of Earth Prospecting and Information Technology | Li X.,University of Science and Technology of China | Zhong W.,University of Science and Technology of China
Journal of Convergence Information Technology | Year: 2012

The Track Methodology Model (TMM) proposed one ontology dynamical building method, which includes ontologies (Top-level Ontology, Domain Ontology and Application Ontology) and five stages in the process of ontology building (analysis, design, development, deployment and evaluation). According to the dynamical process of ontology creating and evolving, the TMM explored the qualitative analysis on the above three categories of ontologies and their relationships. Based on the TMM, some applications of knowledge ontology have been created and executed successfully. Hence, the TMM can instruct efficiently the process of ontology building and knowledge sharing.


Wang R.-J.,China University of Petroleum - Beijing | Wang R.-J.,Key Laboratory of Earth Prospecting and Information Technology | Qiao W.-X.,China University of Petroleum - Beijing | Qiao W.-X.,Key Laboratory of Earth Prospecting and Information Technology | And 4 more authors.
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2013

We firstly made several TI borehole model wells, and measured the compressional, shear velocities and density of the material. The equivalent TI elastic parameters were obtained by a fast simulated annealing algorithm. Then we simulated dipole acoustic logging by ultrasonic measurement experiments in the borehole surrounded by a HTI formation using small-scale dipole transducers. Combined with numerical simulation results, the influence of the orientation of dipole sources on acoustic logging response is analyzed. The results showed that the amplitude and velocity of flexural waves changes with the orientation of dipole sources. The amplitude of cross-line waveforms gets the minimum when the orientation of dipole sources is perpendicular or parallel to the fast shear direction, and is relative large when the angle between the orientation of dipole sources and the fast shear direction is neither 90° nor 0°. The variation of inline waveform amplitude is contrary to that of the cross-line waveforms. When the angle between the orientation of dipole sources and the fast shear direction is less than 30° or greater than 60°, the velocity of the flexural waves is close to that of fast flexural waves and slow flexural waves respectively, and it is not sensitive to the angle. When the angle is between 30° and 60°, the velocity is quite sensitive to the angle, and rapidly changes from the velocity of fast flexural waves to the velocity of slow flexural waves as the angle increases.


Wang R.-J.,China University of Petroleum - Beijing | Wang R.-J.,Key Laboratory of Earth Prospecting and Information Technology | Qiao W.-X.,China University of Petroleum - Beijing | Qiao W.-X.,Key Laboratory of Earth Prospecting and Information Technology
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2015

Acoustic logging while drilling (LWD) is able to provide real-time acoustic properties of rock formations near bits, and therefore has an incomparable advantage over acoustic wireline logging (WL) in saving wellbore occupation time and avoiding risks. Current quadrupole acoustic LWD is capable of measuring formation shear velocity in arbitrary rock formations. However, the quadrupole acoustic LWD theory is not complete yet, i.e., there is no clear understanding on some fundamentals, which required further study. We derive the dispersion equations for the waveguide consisting of a fluid-filled borehole surrounded by a VTI formation, and numerically calculate the dispersion, amplitude and sensitivity functions of the borehole modes excited by a quadrupole acoustic source. We also synthesize the array waveforms recorded by the receivers in the borehole. The influences of formation anisotropy on borehole quadrupole modes are investigated. Numerical results show that, the formation anisotropy has negligible effects on the collar modes, while it strongly affects the formation modes. Only at a few frequencies, the control factor is simple, such as at the cut-off frequency of screw waves. The formation quadrupole modes of the lowest order show significant response to the formation shear velocity within approximate 2 borehole radii away from the sidewall, and it can be utilized to perform the radial tomography of shear velocity in this radial range. For fast formations, the first arrival includes borehole refracted shear mode, part of F1 and F2 modes, the velocities of which are close to that of shear modes, and it can be utilized to accurately evaluate the formation shear velocity without the influence of formation anisotropy. In slow formations, the formation screw modes are highly influenced by anisotropy. It suggests that, in field data processing, for fast formations, the first arrived wave packet can be utilized to extract shear wave velocity, while for slow formations, the formation screw waves can be processed by data-driven methods to obtain true shear wave velocity of rock formations. Because the operation frequencies for fast and slow formations are different, broadband and high-powered transmitters and high-sensitivity receivers should be adopted in the design of an acoustic LWD tool, to increase the signal-to-noise ratio and to improve application range of the tool. ©, 2015, Science Press. All right reserved.


Wang R.,China University of Petroleum - Beijing | Wang R.,Key Laboratory of Earth Prospecting and Information Technology | Qiao W.,China University of Petroleum - Beijing | Qiao W.,Key Laboratory of Earth Prospecting and Information Technology
Shengxue Xuebao/Acta Acustica | Year: 2016

We study acoustic wave field in a fluid-filled borehole associated with a TI formation produced by a phased arc array source, and analyze the sensitivity of this source to azimuthal anisotropy of formation shear waves in order to develop a new anisotropy evaluation method. Results show that this source is able to generate acoustic field of multi-azimuthal order, and the primary acoustic modes are the monopole modes and dipole modes. In HTI formations, the waves excited by sources with different radiation azimuths propagate with different velocities. The azimuthal sensitivity of phased arc array to formation shear anisotropy is mainly contributed by flexural modes produced by this source. Compared to a traditional cross-dipole source, the phased arc array transmitter can be used to evaluate formation heterogeneity and increase the measurement number around the borehole decreasing uncertainty of inverted results. Additionally, this source has the function of multipole sources. Therefore, it is possible to obtain the most reliable anisotropy measurements by using optimized phased control strategy with this source. © 2016 Acta Acustica.

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