Interpretation Of Logging Data Research Articles

Interpretation of wireline log data for reservoir characterization of the Rashidpur Gas Field, Bengal Basin, Bangladesh.

The study was embodied with quantitative analysis of petrophysical parameters of the gas zone to characterize the reservoirs in the Rashidpur well-4 of the Rashipdur Gas Field, Bangladesh. 20 permeable zones were identified in the study. Among these, 4 zones were gas-bearing and the rest zones were water. Hydrocarbon type might be gas which was positively indicated comparatively high resistivity, low neutron and low density log responses in these zones than that of the water zones. Average porosity of these zones ranged from 18-27 %, water saturation 17-40 %, hydrocarbon saturation 60-82 % and permeability ranged from 50.94 mD to 363 mD. Hydrocarbon is moveable in the reservoir because all the value is less than 0.70 indicate by hydrocarbon moveavility index. Average bulk volume of water ranged from 0.04 to 0.13. All the calculated values support that lithology are fine to very fine-grained sandstone and is at irreducible water saturation. The zone-4 was shown comparatively highest thickness, porosity, hydrocarbon saturation and permeability than other zones. The study can be concluded that these hydrocarbon-bearing zones are potential for gas production and good reservoir bearing formation.

Seismic reflection, distribution, and potential trap of Permian volcanic rocks in the Tahe field

Permian Kaipaileicike (开派雷兹克) volcanic rocks approximately 0–200 m thick are drilled in the Tahe (塔河) field. The distribution of volcanic rocks and their potential to form hydrocarbon reservoirs are discussed based on the integrated interpretation of log and 3D seismic data. The volcanic rocks, mainly consisting of dacites and basalts, are sandwiched between the Lower Triassic and Lower Carboniferous and bounded by top and bottom unconformities. The dacites accumulated in a mound shape around volcanic craters, whereas the basalts are deposited in tabular or trough-fill geometries. Permian volcanic craters mainly located at the northwest corner of the Tahe field are identified from volcanic rock thickening, occurrence of volcanic breccias, structural arch of the top Permian, seismic attribute anomalies, and fault (piercing conduit) reflections. Along the northwest wing of a Carboniferous salt dome, a stratigraphic trap is formed by a northeast updip pinch-out of Permian volcanic rock. Oil indications within the trap are found in numerous wells. The reservoir volcanic rocks are mainly of the fracture-pore pattern and covered by the caprock of a Lower Triassic mudstone. The hydrocarbon reservoir, which can potentially be a medium-sized oil pool, is connected to Cambrian-Ordovician source rocks through normal faults along the salt dome boundary.

Removal of Cyclic Borehole Noise From Low- and High-Resolution LWD Images and Its Impact on Image Interpretation

Summary The use of logging-while-drilling (LWD) imaging tools in realtime decision making and post-drilling analysis has become commonplace. However, image noise and processing errors because of inherent measurement physics can propagate errors and, thus, complicate interpretation of openhole log data and images. For example, standard density images tend to amplify image noise from small borehole irregularities. Among different borehole irregularities, spiraling is known to occur more frequently with conventional rotary assemblies, steerable motor assemblies, and rotary-steerable assemblies. When the cyclic-noise amplitude from spiraling becomes large relative to the measurement of the primary interest, it grossly affects the quality of the recorded formation bulk density, photoelectric factor, and neutron porosity. This paper shows novel methods to remove cyclic noise from formation-evaluation (FE) images by applying frequency-domain filtering. Although the initial attempt of fast Fourier transforms (Zhang et al. 2010) illustrates the straightforward concept, it is seldom used because of implementation issues requiring interactive filter design and intensive operator intervention. Recently, a new method (Sugiura et al. 2011) has been designed to improve the filtering process. Additionally, the new adaptive filter designs automate the cyclic-noise-removal process from the FE images. Standalone software has been developed to process the entire image logs from one well, without human supervision. The software adaptively modifies the filter behavior as borehole-oscillation noise characteristics change with formation, drilling assemblies, hole inclination, and depth. To examine its validity qualitatively, the algorithm is then applied to various field data, not only on low-resolution density images but also on higher-resolution density images. The new algorithm has been proved by bringing considerable improvement to the image quality without any artificial interruptions. The rugosity effect is reduced significantly, and the apparent resolution of bed-boundary features is increased. Furthermore, comparative field examples illustrate the improvement in image-feature extraction. The method described here is critical, for example, for small-fracture detection and more-precise definition of formation-property contrasts indicative of bed boundaries in irregular boreholes. This new method not only is effectively used for density images but also is applicable to any other borehole images, such as resistivity and ultrasonic images.

Mineral Compositional Trends and Their Correlations with Petrophysical and Well-Logging Parameters Revealed by Quanta + Bestmin Analysis: Miocene of the Carpathian Foredeep, Poland

AbstractThis study uses the data from Miocene rocks of the Carpathian Foredeep to test the performance of the computer programs QUANTA and BESTMIN in aiding the interpretation of geophysical log data. These programs were designed to help trace trends in the mineral composition of rocks, the chemical composition of minerals, and the effects of these data on petrophysical and geophysical logging parameters. Chemical and X-ray diffraction data for 65 samples of shales, sandstones, and carbonates taken from cored wells in the molasse basin of the Carpathian Foredeep were processed. Compositional differences were detected between rocks sourced from the platform and rocks sourced from the Carpathians. Quartz, K-feldspar, and zircon were more abundant in the coarse-grained rocks (sandstones), while calcite, ankerite, siderite, pyrite, barite, halite, celestite, apatite, anatase, chlorite, 2:1 minerals, and organic matter were more abundant in the fine-grained rocks (shales). Plagioclase reached its maximum in coarse shales. Ankerite, chlorite, and dioctahedral 2:1 minerals had more Fe in the coarse-grained rocks. The dioctahedral 2:1 minerals in fine-grained rocks had a greater concentration of smectitic layers. This information permitted the precise calculation of grain density, porosity, adsorbed water, and some geophysical logging parameters. It also permitted the calibration of well-log response, in particular, the macroscopic neutron absorption cross-section (Σa) combined with the photoelectric absorption factor (P{e}) or with Pe + Ca (calcium content, measurable in wells by spectroscopic techniques) with porosity and cation exchange capacity (CEC). The NaCl concentration in the pore waters was found to range from the values typical for seawater in shales to the freshwater level in clean sandstones.

Corrections for downhole NMR logging

Nuclear magnetic resonance logging (NMR) is an open well logging method. Drilling mud resistivity, formation resistivity and sodium ions influence its radio frequency (RF) field strength and NMR logging signals. Research on these effects can provide an important basis for NMR logging data acquisition and interpretation. Three models, water-based drilling mud—water bearing formation, water-based drilling mud—oil bearing formation, oil-based drilling mud—water bearing formation, were studied by finite element method numerical simulation. The influences of drilling mud resistivity and formation resistivity on the NMR logging tool RF field and the influences of sodium ions on the NMR logging signals were simulated numerically. On the basis of analysis, RF field correction and sodium ion correction formulae were proposed and their application range was also discussed. The results indicate that when drilling mud resistivity and formation resistivity are 0.02 Ω·m and 0.2 Ω·m respectively, the attenuation index of centric NMR logging tool is 8.9% and 9.47% respectively. The RF field of an eccentric NMR logging tool is affected mainly by formation resistivity. When formation resistivity is 0.1 Ω·m, the attenuation index is 17.5%. For centric NMR logging tools, the signals coming from sodium ions can be up to 31.8% of total signal. Suggestions are proposed for further research into NMR logging tool correction method and response characteristics.

Application of OpenMP to Wireline Triaxial Induction Logging in 1D Layered Anisotropic Medium

Efficient and accurate forward modeling of logging tool responses is essential for data inversion in the log data interpretation in both real time and postprocessing. With the aggressive advancement of various high-performance computing techniques and computer hardware technology, it is possible to significantly improve the efficiency of the forward modeling. In this paper, we apply OpenMP to parallelize the simulation of triaxial induction logging tools in 1D multilayered anisotropic formation. The parallel process is explained in detail and numerical examples are presented to demonstrate the effect of the parallel programming. Comparison of the original code and the parallel code shows that the latter is much faster without loss of accuracy, which is very promising for future real-time inversion.

Parameter Response Numerical Simulation of Resistivity LWD Instrument Based on Hp-FEM

Numerical simulation of electrical logging is important to the electrical logging instrument design and logging data interpretation and application. In this paper, we combine the hp finite element method (hp-FEM) analysis software HERMES and VC++ development platform as a tool to direct reflect the instrument drilling detection and distribution of induced electric field in the formation and it's boundary, and the instrument parameter response by changing spacing, transmitting frequency and excitation current intensity have been studied based on self-adaptive hp-FEM algorithm. Because the performance of resistivity LWD instrument have decided by design parameters, thus study the electromagnetic response characteristics of resistivity LWD instrument has important significance to guide the high precision resistivity LWD instrument develop and improve the security of logging operation.

Особенности интерпретации материалов каротажа по новым скважинам

Особенности интерпретации материалов каротажа по новым скважинам

Experimental study of gas-water elongated bubble flow during production logging

In order to improve the interpretation of production log data on gas-water elongated bubble (EB) flow in horizontal wells, a multi-phase flow simulation device was set up to conduct a series of measurement experiments using air and tap water as test media, which were measured using a real production logging tool (PLT) string at different deviations and in different mixed flow state s. By understanding the characteristics and mechanisms of gas-water EB flow in transparent experimental boreholes during production logging, combined with an analysis of the production log response characteristics and experimental production logging flow pattern maps, a method for flow pattern identification relying on log responses and a drift-flux model wer e proposed for gas-water EB flow. This m odel, built upon experimental data of EB flow, reveals physical mechanisms of gas-water EB flow during measurement processing. Th e coefficients it contains are the specific values under experimental conditions and with the PLT string used in our experiments. These coefficients also reveal the interference with original downhole flow patterns by the PLT string. Due to the representativeness that our simulated flow experiments and PLT string possess, the model coefficients can be applied as empirical values of logging interpretation model parameters directly to real production logging data interpretation, when the measurement circumstances and PLT strings are similar.

Thermal properties of rocks of the borehole Yaxcopoil-1 (Impact Crater Chicxulub, Mexico)

SUMMARY The results of thermal property measurements on cores from the scientific well Yaxcopoil-1 (1511 m in depth) drilled in the Chicxulub impact structure (Mexico) are described. The thermal conductivity, thermal diffusivity, volumetric heat capacity, thermal anisotropy coefficient, thermal heterogeneity factor, and, in addition, porosity and density were measured on 451 dry and water-saturated cores from the depth interval of 404–1511 m. The acoustic velocities were determined on a subgroup of representative samples. Significant vertical short- and long-scale variations of physical properties related to the grade of shock-thermal metamorphism and correlations between thermal and other physical properties are established. Rocks of the post-impact and impact complexes differ significantly in heterogeneity demonstrating that the impact complex has larger micro- heterogeneity on sample scale. The pre-impact rocks differ essentially from the impact and post-impact rocks in the thermal conductivity, thermal diffusivity, density and porosity. The thermal anisotropy of rocks of all structural-lithological complexes is very low (K = 1.02 … 1.08), which is similar to the situation in the Puchezh-Katunk and Ries impact structures. Correlations are established between the thermal conductivity and elastic wave velocities measured in laboratory. For limestone-calcarenites, the thermal conductivity (λ) can be calculated from the compressional wave velocity (Vp) using the formula λ= 0.346 Vp + 0.844, and for dolomite-anhydrites this relation has the form λ= 0.998 Vp + 1.163 [for λ in W (m K)−1 and Vp in km s−1]. These correlations are used for downscaling of the sonic velocities to the decimetre scale. The effective medium theory is applied to invert the matrix thermal conductivity and pore/crack geometry from the thermal conductivity measured on the studied samples. Representative experimental data on the thermal properties for all lithological groups encountered by the Yaxcopoil-1 well essentially extend an existing database on the thermal properties of rocks of impact structures and can be used for determination of the heat flow density, interpretation of temperature logging data, theoretical modelling of heat and mass transfer processes and constructing thermal models of the Chicxulub impact structure as well as for the lithological interpretation. The research results confirm the necessity of dense sampling for the thermal property measurements to obtain reliable results in petrophysical and geothermal investigations of impact structure formations.

Microstructural controls on electric and acoustic properties in tight gas sandstones; some empirical data and observations

Quantitative interpretation of log data from tight gas sandstone reservoirs is almost always difficult, and typically yields saturations that are inconsistent with results from various measurements of well performance. This is an issue of economic importance, as the ability to use log data to reliably identify completion zones and predict well performance could result in considerable cost savings for operators.

Down the borehole but outside the box: innovative approaches to wireline log data interpretation

Down the borehole but outside the box: innovative approaches to wireline log data interpretation

Technology Focus: Formation Evaluation (August 2010)

Technology Focus Analysts of conventional logs, who routinely evaluate complex formations, may be less productive when faced with more-esoteric responses from modern tools, especially because the latter often are interpreted by the logging contractors themselves. This situation arises because available petrophysical software may not be capable of handling the new log responses, and the required interpretive algorithms often are claimed as proprietary and, therefore, are withheld. Logging-contractor-generated results from new logs may bring additional insight that is not readily apparent from basic logging suites, but end users must beware of blindly accepting these results and the implication that the new tools are necessary. Many published case studies that claim new logging services are essential do not prove that basic logs are inadequate. Readers should be skeptical if these conference papers do not conform to Richard Feynman’s exhortation, “The idea is to try and give all the information to help others to judge the value of your contribution, not just the information that leads to judgment in one particular direction or another.” We should always ask ourselves three questions: Was the log really necessary? Does it add new information or simply confirm what could have been determined from a basic logging suite? For example, a nuclear-magnetic-resonance log in shaly gas-bearing sands with oil-based-mud-filtrate invasion may be able to distinguish gas from oil, but invaded-zone fluids also can be solved for by use of a combination of conventional logs. Is the logging-contractor interpretation correct? New logs should be validated against careful traditional-log analysis, which has been calibrated against core. Can operators improve on the logging-contractor interpretation? Yes! Operators have more relevant data and local knowledge, so they can use the log data more effectively. Petrophysical software and a log analyst’s time cost much less than log acquisition. Logging contractors should run a safe and efficient operation while acquiring good raw data. If they also can supply an interpretation, then this is a bonus. End users must not abdicate their responsibility for the interpretation of log data that their employer pays to acquire. Formation Evaluation additional reading available at OnePetro: www.onepetro.org SPE 125342 • “Reservoir-Rock-Types Application—Kashagan” by A. Francesconi, Eni, et al. SPE 128013 • “Residual Hydrocarbons—A Trap for the Unwary” by T. O’Sullivan, SPE, Cairn India, et al. SPE 130414 • “Fulmar Sandstones—Correcting Some Received Wisdom in the Greater Kittiwake Area (North Sea)” by G. Coghlan, SPE, Centrica Energy, et al.

Lateral contrast and prediction of carboniferous reservoirs using logging data in Tahe oilfield, Xinjiang, China

Valuable industrial oil and gas were discovered in the formations of Ordovician, Carboniferous and Triassic of the Tahe (塔河) oilfield, Xinjiang (新疆), China. The Carboniferous formations contain several oil- and gas-bearing layers. The lateral distribution of Carboniferous reservoir is unstable, and thin layers are crossbedded. This makes it difficult to do lateral formations’ contrast and reservoir prediction, so it is necessary to develop a method that can achieve reservoir lateral contrast and prediction by using multi-well logging data and seismic data. To achieve reservoir lateral contrast and prediction at the Carboniferous formations of the Tahe oilfield, processing and interpretation of logging data from a single well were done first. The processing and interpretation include log pretreatment, environmental correction and computation of reservoir’s parameters (porosity, clay content, water saturation, etc.). Based on the previous work, the data file of logging information of multi-well was formed, and then the lateral distribution pictures (2D and 3D pictures of log curves and reservoir parameters) can be drawn. Comparing multi-well’s logging information, seismic profiles and geological information (sedimentary sign), the reservoir of the Carboniferous in the Tahe oilfield can be contrasted and predicted laterally. The sand formation of Carboniferous can be subdivided. The results of reservoir contrast and prediction of the Carboniferous formations show that 2D and 3D pictures of multi-well reservoir parameters make the lateral distribution of reservoir and oil-bearing sand very clear, the connectedness of the reservoir of neighboring wells can be analyzed, and five sand bodies can be identified based on the reservoir’s lateral distribution, geological information and seismic data.

A Forward Modeling Approach for Interpreting Impeller Flow Logs

A rigorous and practical approach for interpretation of impeller flow log data to determine vertical variations in hydraulic conductivity is presented and applied to two well logs from a Chalk aquifer in England. Impeller flow logging involves measuring vertical flow speed in a pumped well and using changes in flow with depth to infer the locations and magnitudes of inflows into the well. However, the measured flow logs are typically noisy, which leads to spurious hydraulic conductivity values where simplistic interpretation approaches are applied. In this study, a new method for interpretation is presented, which first defines a series of physical models for hydraulic conductivity variation with depth and then fits the models to the data, using a regression technique. Some of the models will be rejected as they are physically unrealistic. The best model is then selected from the remaining models using a maximum likelihood approach. This balances model complexity against fit, for example, using Akaike's Information Criterion.

Blocking geophysical borehole log data using the continuous wavelet transform

The interpretation of geophysical log data is frequently difficult due to the noisy downhole environment. Blocking algorithms attempt to smooth the log data while leaving the boundaries between different geological units sharp. This paper introduces a method for the determination of the boundaries based on the zero contour of the continuous wavelet transform (CWT) of the data. The amount of blocking can be controlled by the choice of the scale of the wavelet used. The method is compared with results from the median filter and with discrete wavelet transform (DWT) blocking methods, and is here applied to log data from Australia. The application of the new CWT method overcomes the rounding and shifting of boundaries inherent in median filtering, and provides greater flexibility by overcoming the power of two limitations in the DWT log blocking.

Utilization of drill cuttings for interpretation of logging data in carbonate-rock oil and gas fields

Utilization of drill cuttings for interpretation of logging data in carbonate-rock oil and gas fields

Statistical Segmentation of Geophysical Log Data

Stationary segments in well log sequences can be automatically detected by searching for change points in the data. These change points, which correspond to abrupt changes in the statistical nature of the underlying process, can be identified by analysing the probability density functions of two adjacent sub-samples as they move along the data sequence. A statistical test is used to set a significance level of the probability that the two distributions are the same, thus providing a means to decide how many segments comprise the data by keeping those change points that yield low probabilities. Data from the Ocean Drilling Program were analysed, where a high correlation between the available core-log lithology interpretation and the statistical segmentation was observed. Results show that the proposed algorithm can be used as an auxiliary tool in the analysis and interpretation of geophysical log data for the identification of lithology units and sequences.

Experimental study on core permittivity of Xinjiang oilfield

This paper introduces the principles and procedures of the core permittivity measurement using a parallel capacitor with an electromagnetic shield. The cores from the Xinjiang oilfield were measured by using the frequency-swept method at different salinities and saturations. The effects of salinity, frequency, porosity and saturation on core permittivity were investigated. The relationship of core permittivity versus water saturation and the relationship of dry core permittivity versus porosity were obtained. The permittivity values of rock matrix and oil were obtained at a frequency of 47 MHz and 200 MHz, and would provide guidance for the interpretation of dual frequency dielectric logging data.

Petroleum potential of reservoirs at the Paleozoic-Mesozoic boundary in West Siberia: seismogeological criteria ( example of the Chuzik-Chizhapka regional oil-gas accumulation)

The study aims at developing petroleum potential criteria for reservoirs at the Paleozoic-Mesozoic boundary in West Siberia, by the example of the Chuzik-Chizhapka regional oil and gas accumulation in the Parabel District (Tomsk Region). Oil and gas accumulations in formations of the Paleozoic-Mesozoic boundary were discovered in the Archa, Urman, Gerasimovka, Kalinovoe, North Kalinovoe, Tambai, Ostanino, North Ostanino, and other fields within the Chuzik-Chizhapka zone. Hydrocarbons are hosted by reservoirs of different lithologies and ages, including Devonian and Carboniferous organic, dolomite, and siliceous limestones and argillaceous-siliceous rocks. Synthetic interpretation of seismic profiling and log data was used to model the geological structure of the Chuzik-Chizhapka regional accumulation, to develop potential criteria for reservoirs of the Paleozoic basement and weathering zone, and to suggest methods for detection of complex traps in upper Paleozoic strata.