Lateral Log Research Articles

Integration of completion data, microseismic data, downhole logs, and multicomponent seismic data in the Mississippi Lime, north-central Oklahoma

Previously published work on a Mississippi Limestone (Mississippi Lime) prospect in north-central Oklahoma described a prospect that is data rich. Aquisition was on a dense grid using nodal 3C phones, and PP and PS data were both processed and jointly inverted. Several pilot holes and laterals were drilled and fully logged, including Sonic Scanner and formation-microimager (FMI) fracture logs. Microseismic data were acquired on one well pad, as was a 3D VSP. New resesarch discusses two specific fracture-characterization methodologies. The first is the integration of vertical and lateral log suites, including fracture imaging, with seismic rock properties and completion results, including microseismic data. The results of this effort not only characterize fracture width and height but go farther by explaining why and how those fractures are created. The second is the use of converted-shear (PS) data to measure anisotropy and correlate those measurements with fracture logs. Specifically, two methods of calculating anisotropy are analyzed: slow shear-wave (S2) traveltime correction and transverse/radial energy ratio. Both methods are theoretically valid but might break down in practice because of various nongeologic artifacts that can be present in the data.

Numerical Simulation of Dual Laterolog in Cavernous Carbonatite Reservoir

Zhao, J.; Wang, D., and Gu, H., 2015. Numerical simulation of dual laterolog in cavernous carbonatite reservoir.The cavernous reservoir has become one of the main carbonate reservoirs for stable and increasing production. The degrees and the types of fillings materials are the key factors which affect the characteristics of accumulation and flowage. However, due to the complexity of fillings in the caves, the response laws of logging of the cavernous reservoir can not be understood clearly and its effective evaluation has been severely hampered. This paper uses for the first time numerical simulation to study the responses in the curve of dual lateral log of cavernous reservoir. By establishing a continuous equation of the dual lateral log and its boundary factors and using the electric field superimpose principle, a finite element method is used to study the cave size, different filling agents and degrees are simulated. The result indicates that the size, filling agents and degrees show a clear response, and they have a clear correspondence. Summarizing and analyzing the response laws on the dual lateral logging curves of the cavernous reservoir can provide theoretical evidence for the logging evaluation of the carbonate cavernous reservoir.

The Application of Phase-Sensitive Detection Technology in the Lateral Logging

In the course of logging, the instrument needs to measure the formation parameters, at the same time we need to solve the problem that the various signals with different frequencies will be produced. The technology with the use of phase sensitive detection filter can reduce mutual interference between the various signals, which can achieve the purpose of improving the measurement accuracy. This paper analyzed the work principal of phase sensitive detection technique in lateral logging applications, the data shows that this method can effectively eliminate or reduce the impact phase, thereby improving the measurement accuracy of lateral logging instrument.

Formation evaluation case study: Glyde unconventional Middle Proterozoic play in the McArthur Basin, northern Australia

The Glyde–1 and Glyde Sidetrack–1 wells were drilled by Armour Energy in the Glyde Sub-basin of the McArthur Basin, NT, Australia in August 2012. This program was to evaluate the unconventional hydrocarbon potential of the Barney Creek Shale source rock and the conventional potential of the Coxco Dolomite of the McArthur Group. The Glyde wells discovered gas in both formations. Transtensional faults in this region allowed to form a series of fault-bounded depocentres. The target gas source of the Glyde discovery is located in 1640 Ma organic-rich black shales of the Barney Creek Formation. Weatherford was contracted to acquire both vertical and lateral advanced log suites and perform subsequent log interpretation to constrain the in situ minimum and maximum horizontal stress regimes to assist with maximising gas production from future lateral placement pilot programs in the Coxco Hydrothermal Dolomite (HTD) Play. Two stratigraphic and structural domains were defined by the observed features in the image log data; a dolostone dominated, fractured strata below an erosional surface. Above this stratigraphic timeline is a monotonous package of laminated, lower-energy Barney Creek Formation sediments. Observed changes in azimuths and dips of the measured beddings suggest a phase of compression after deposition of the Barney Creek Formation, resulting in gentle folding of the formations. The porous gas-charged HTD play is drilled in top of the anticline, which is further characterised by a significant number of conductive fractures, likely indicative of open fractures.

Evaluation of the coal reservoir permeability using well logging data and its application in the Weibei coalbed methane field, southeast Ordos basin, China

Permeability is one of the most critical reservoir evaluation parameters in coalbed methane (CBM) exploration and development. In this study, an improved collection of sheets model was proposed for evaluation of reservoir permeability of the no. 5 coal seam in the Weibei CBM field, southeast Ordos basin, China. The evaluation model is expressed by k = 8.50 × 10− 4 nw 2 ϕ f in which the fracture width (w), fracture density (n), and porosity (φ f) can be obtained by analysis of the deep lateral resistivity logging and micro-sphere focusing logging data. The calculated permeability values are ranging from 0.005 to 2.327 mD across the Weibei coalfield. The regional distribution of permeability is mainly controlled by the factors of burial depth and tectonics stress. The permeability is high in the shallow area and the zone of normal faults, but it is low in the anticline area and the upthrust side of thrust faults. The results show that the calculation method developed in this study is reliable, providing a better understanding of the coal reservoir for CBM exploration in the study area.

METHOD FOR AUTOMATED QUALITY CONTROL LOG DATA

This work is devoted to the development of scientific principles, methods and techniques of automated control of the primary data recorded in geophysical research in the wells (GIS). The problem of providing high quality interpretation of geophysical data has always been one of the most important tasks of the oilfield geophysics; therefore, one of the areas indicated in solving the problem is to increase the accuracy and reliability of the GIS data. The first evaluation of materials by the operator on the Exploration wells directly on the site, which requires considerable knowledge of the theory of GIS techniques and a lot of experience. The issue of termination of logging on certain well connected with the expert expressed confidence in getting quality of the research results. However, most operators either do not have the required qualifications or are not able to assess the quality due to the large amount of data, the study of complex conditions, etc. Relevance of the use of automated tools to detect errors and quality control of recorded data during or immediately upon completion of studies argued sharply increasing price of write errors with each subsequent milestone. The article gives a brief overview of features unreliability of tracks and the currently existing approaches to the problem of quality control of GIS data identified a number of shortcomings of the methods considered. A design of the heuristic algorithm for solving the problem of quality control data using data recovery techniques with spaces.Formulated gradient criterion similarity measure fragments of recordings of logs. The results of numerical experiment on automatic data verification lateral logging.

Log evaluation of a coalbed methane (CBM) reservoir: a case study in the southern Qinshui basin, China

Proximate analysis components, gas content, porosity and permeability are the most important parameters for CBM reservoir evaluation. Based on the analysis of the conventional well log response of the no. 3 and no. 15 CBM seams in the southern Qinshui basin of China, regression analysis is used to establish the prediction models of the components of proximate analysis. The Langmuir rank equation is used to calculate the gas content. Variable matrix density is used to evaluate the total porosity. Based on the dual lateral log interaction method, a fracture porosity estimation model is established and the coal fracture permeability is predicted by using the Faivre–Sibbit method in the two CBM seams. Comparisons between the estimated and measured data of proximate analysis components, gas content, porosity and permeability indicate that the established models are credible. The absolute errors between the estimated moisture (Mad), ash (Aad), volatile (Vdaf), fixed carbon (FCad) and the measured results of coal in two coal seams are less than 0.41%, 9.47%, 3.61% and 9.41%, respectively. The absolute errors between the estimated and measured gas content are less than 4.05 cm3 g-1. The absolute errors of estimated total porosity and the analysed results of coal are less than 0.84%. Field samples show that Mad, Aad and Vdaf are less than 1.00%, 10.00%–25.00% and 10.00–15.00%, respectively, in the no. 3 and no. 15 CBM seams in the southern Qinshui basin. The FCad is close to 70.00%. The gas content ranges from 7.00 cm3 g-1 to 20.00 cm3 g-1 in the no. 3 coal seam and from 10.00 cm3 g-1 to 30.00 cm3 g-1 in the no. 15 coal seam. The total porosity is close to 5.50% and the fracture porosity is generally less than 2.50%. Fracture permeability is mainly distributed from 0.001 to 10 mD. The results indicate that the conventional well logs are effective in CBM reservoir evaluation.

Petrophysical Study on Carbonate Reservoir

In light of complex lithology and serious heterogeneity of carbonate reservoir, the paper presents a comprehensive study of petrophysical characteristics of it. By using available well log data and fuzzy mathematical method, a lithologic model for identification of carbonate reservoir is developed. According to recognized fractural types, a model for fractural porosity interpretation is established. By way of correction of small core sample using big sample, relationship between core porosity and effectively estimated well log porosity is built up, obtaining effective porosities. Using different fractural types and dual lateral log data, a model for fluid saturation explanation is set up. Furthermore, these models and measured information are used for feasibility evaluation of them, reaching higher consistency and satisfied results.

Distribution Characteristics of Structural-Deformed Coal in Southern Shizhuang Block, Qinshui Basin

The research of structural-deformed coal is important in coalbed methane exploitation. Compared with those of undeformed coals, the geophysical logging characteristics of structural-deformed coals show lower amplitude value of deep lateral log (LLD) and density log (RHOB) and higher amplitude value of acoustic log (AC). In the southern Shizhuang Block, the structural-deformed coal is commonly developed, with the thickness ranging from 0.6 to 1.1 m. The thickness of structural-deformed coals accounts for 11.5-18.5% of the total coal thickness. In general, the structural-deformed coals are more developed in the west than those in the east of the study area.

Body Wave Velocities Estimation From Wireline Log Data Utilizing an Artificial Neural Network for a Carbonate Reservoir, South Iran

Reservoir characterization is a prerequisite study for oil and gas field development. Body wave velocities are important parameters for reservoir characterization studies. In this research, a back-propagation artificial neural network (BP-ANN) including the Levenberg-Marquardt training algorithm was used as an intelligent tool to estimate compressional and shear wave velocities. The efficiency of utilizing density log and photoelectric effect (PEF) in improving estimation accuracy have been evaluated as well. The petrophysical data from three wells were used for constructing intelligent models in the South Pars field, Southern Iran. The fourth and fifth wells from the field were used to evaluate the reliability of the model. The results showed that a BP-ANN was successful in estimating body wave velocities and so when just gamma ray, neutron, deep resistivity (lateral log deep) were used as net work inputs, the net exactness ware comparatively low but using PEF effects increased this exactness. By using density log the net exactness noticeably grew and in this manner using both PEF and density log beside other mentioned logs as inputs approached to more real results.

The High Resolution Three Lateral Logging Response Research Based on MATLA

The formation resistivity is a main parameter in logging interpretation and evaluation of oil and gas reservoir. And high resolution three-lateral logging is an important measuring method in resistivity logging. According to the present finite element program for three lateral logging concludes data and the powerful graphics capabilities of MATLAB, we study the relationship between potential or current and focusing characteristics. The results are important for how to design equipment parameters, and control the current focus to achieve the best focusing.

ГЕОДИНАМІКА

Two types of lateral logging equipment for geophysical investigations of horizontal wells are proposed. Effective solution algorithms for lateral logging 3D direct and inverse problems are described.

Modelling approaches for the estimation of irreducible water saturation and heterogeneities of the commercial Ashtart reservoir from the Gulf of Gabès, Tunisia

A bstract Oil production based on reserves in place in the Ashtart oilfield required the precise knowledge of the main reservoir parameters including porosity, permeability and irreducible water saturation. The reservoir series is comprised of Nummulitid but heterogeneous limestones of the El Garia Formation, the petrofacies texture, geometry and petrophysical parameters of which were apprehended using seismic profiles; gamma-ray and sonic lateral logs, as well as cores and cuttings taken in drillwells. The evaluation of residual oil saturation, multiphase flow and oil production techniques from the Ashtart reservoir also depend on variations and zoning of the irreducible water saturation. Estimation of the initial water saturation and hence variations in the capillary pressure in the reservoir, required compilations of porosity data measured on cores, supplemented by additional but computed porosities based on acoustic log diagrams. Furthermore, Gamma Ray, Sonic log, and well to well correlations tied to core results and well cuttings, help recognize the layered lithologies within the El Garia flat lying but stratified, Ypresian in origin reservoir rocks. Abundant permeability and porosity values compiled in the light of seismic sequence and Gamma Ray and Sonic log details, were integrated in an empirical approach using the Leverett J function, to model the irreducible water saturation depending on the capillary pressure distribution in the whole reservoir. Variations of this principal hydraulic parameter in a wide range (S w ir : 12 to 40%) compared to the preceding lithostratigraphic, petrographical and petrophysical results help recognize four main rock pore types in the commercial Ashtart reservoir. These vary from (1) a zone with a rock pore type showing an irreducible water saturation as low as 12%, and a fairly good reservoir character in the lower third part of the lithologic column which is thought to channelize a multiphase fluid flow in the global oilfield, (2) to those zones built-up of rock pore types with higher initial water saturation amounts which in certain cases tend to indicate zones of degraded reservoir. Our study suggests that diagenesis prevalently controls porosity, due to operative dissolutions of the Nummulitid tests/bioclasts, and cementation; moreover, diagenesis exerts effects on permeability by interconnecting intergranular and intratest pore spaces. In contrast, microfracturing enhances permeability of the reservoir. This is notably the case in the fairly permeable central zone in the Ashtart reservoir with excellent petrophysical parameters, but which were found to degrade gradually towards its peripheries.

Response characteristics of array lateral logs and their primary inversion in reservoirs with fracture-induced anisotropy

In order to identify fractured reservoirs and determine their fracture parameters with a high definition array laterolog, we built a fracture-induced anisotropic formation model with a parallel fracture group. The three-dimensional finite element method is used to simulate the responses of the array laterolog, and then the primary inversion method is utilized. Numerical simulation shows that when the fracture spacing is small, the array laterolog response of the fracture group is the same as that of a formation with macroscopic electrical anisotropy. The apparent resistivity of the array laterolog is approximately inversely proportional to fracture porosity. The anisotropy depends on the fracture porosity in the fractured formation, which accordingly results in response variation of the array laterolog. The higher the fracture dip, the larger the apparent resistivity. When the fracture dip is low the difference between the deep and shallow apparent resistivities is small, and when the dip is high the difference turns out to be positive. The fracture parameters were inverted using the Marquardt non-linear least squares method. The results, both fracture porosity and dip show a good match with parameters in the actual formation model. This will promote the application of the array laterolog in evaluating fractured reservoirs.

Application of the triple porosity model in well–log effectiveness estimation of the carbonate reservoir in Tarim oilfield

In carbonate reservoirs, effectiveness estimation using logging data has great challenges. According to the pore structure characteristics of the fractured and vuggy carbonate reservoir, Aguilera and Aguilera [Roberto F. Aguilera and Roberto Aguilera, 2004. A Triple Porosity Model for Petrophysical Analysis of Naturally Fractured Reservoir, Petrophysics, 45(2):157–166.] presented a triple porosity model, in which the secondary porosity was divided into connected fractured (and/or) vuggy porosity and non-connected vuggy porosity. In this paper, a new technology is presented to determine the values of the different porosity in the triple porosity model. Based on lateral logs responses, we derive analytical equations that contain connected fractured (and/or vuggy) porosity, non-connected vuggy porosity, matrix porosity and so on. Using these equations and the conventional log data, we can obtain the petrophysical parameters, such as connected fractured porosity, non-connected vuggy porosity and so on. Then the connected fractured (and/or vuggy) porosity and its percentage in the total porosity are used to indicate the effectiveness of the carbonate reservoir. This method has been applied for the well log interpretation of the 123 testing intervals from the 52 wells in Tarim oil field. Agreement ratio of the interpretation results is 91%, which verifies the validity of the presented method.

Array processing—a new method to detect and correct errors on array resistivity logging tool measurements

In recent years more and more multi-array logging tools, such as the array induction and the array lateralog, are applied in place of conventional logging tools resulting in increased resolution, better radial and vertical sounding capability and other features. Multi-array logging tools acquire several times more individual measurements than conventional logging tools. In addition to new information contained in these data, there is a certain redundancy among the measurements. The sum of the measurements actually composes a large matrix. Providing the measurements are error-free, the elements of this matrix show certain consistencies. Taking advantage of these consistencies, an innovative method is developed to detect and correct errors in the array resistivity logging tool raw measurements, and evaluate the quality of the data. The method can be described in several steps. First, data consistency patterns are identified based on the physics of the measurements. Second, the measurements are compared against the consistency patterns for error and bad data detection. Third, the erroneous data are eliminated and the measurements are re-constructed according to the consistency patterns. Finally, the data quality is evaluated by comparing the raw measurements with the re-constructed measurements. The method can be applied to all array type logging tools, such as array induction tool and array resistivity tool. This paper describes the method and illustrates its application with the High Definition Lateral Log (HDLL, Baker Atlas) instrument. To demonstrate the efficiency of the method, several field examples are shown and discussed.

Neural Approach for Calculating Permeability of Porous Medium

Permeability is one of the most important properties of porousmedia. It is considerably difficult to calculate reservoir permeabilityprecisely by using single well-logging response and simple formulabecause reservoir is of serious heterogeneity, and well-loggingresponse curves are badly affected by many complicated factorsunderground. We propose a neural network method to calculatepermeability of porous media. By improving the algorithm of theback-propagation neural network, convergence speed is enhanced andbetter results can be achieved. A four-layer back-propagation networkis constructed to effectively calculate permeability from well logdata. Spontaneous potential, resistivity of deep lateral log,resistivity of micro-gradient log, resistivity of micro-normal log,Interval transit time of acoustic log and resistivity of shallowlateral log are selected as the inputs, and permeability is selected asthe output. There are 35 and 40 units used in the two hidden layers,respectively. During the training course, the correlation coefficientbetween the calculated permeability and the standard pattern is as highas 0.9937, the average absolute error between them is0.046 μm2 and the average relative error is only 1.93%. Forpractical applications, the average relative error between thecalculated permeability and actual permeability is also as low as about10.0%.

Multi-Exponential Inversion and Laboratory Study of Induced Polarization Relaxation Time Spectra of Shaly Sands

Abstract According to the traditional Induced Polarization (IP) logging method, the IP relaxation time spectrum can give much more information about a reservoir, such as the pore structure, permeability, formation water resistivity, and shaliness. In this paper, the Singular Value Decomposition (SVD) algorithm is used to inverse the IP multi-relaxation data of the rock samples. The appropriate number of relaxation arrangement points in the relaxation data inversion is from 32 to 64. All of the relaxation spectra show a multi-peak shape. IP decay curve measurements have been performed on 30 samples from the Daqing Oil Field using the four-electrode technique. The effects of charging current, charging and discharging time, brine salinity, and water saturation on the relaxation spectra of the rock were analyzed qualitatively, so that we could develop a new IP spectra logging tool that could be used successfully in practice. When we discussed the effect of one parameter on the relaxation time spectra, the others remained fixed. The results show that the relaxation spectrum relates with the charging time, discharging time, and depends strongly on water saturation. The salinity of NaCl brine and the charging current density are shown to have a small influence on the relaxation spectra in the special ranges. Introduction Induced polarization (IP) phenomena were observed more than 80 years ago, which may be caused by metallic minerals or clay Content(1–8). The detection of IP in the time-domain is made by measuring both the maximum voltage during the charging period of a dc current flow, and the transient decay of the electrical potential as a function of time, after the current is turned off. IP logging is traditionally used to determine the formation water resistivity and shaliness parameter (Qv), which is defined as the cation exchange capacity of the shaly sands per unit pore volume(9–12). But up to now, no IP logging has successfully been used commercially to evaluate or locate petroleum reservoirs. The theory analysis shows that the IP relaxation characteristics relate to the pore structure of the rock and the IP decay curve is a superposition of signals coming from all pores with different sizes(13). So, the curve can be fitted with multi-exponential decay function and a relaxation spectrum can be obtained. The spectrum contains much more information than the traditional IP method. The IP spectra of full water-saturated rock gives a quick, easy, and nondestructive way to characterize the rock, such as the pore structure, permeability, and Qv. On the other hand, we can develop a new time-domain IP spectra logging tool. This kind of IP spectra logging can be also used to obtain the formation water resistivity and shaliness parameter, Qv, as the traditional time-domain IP logging tool. In order to transfer the lab results downhole, the borehole effects, such as rugosity and mud, should also be considered. This can be achieved by using focusing technology as well as technologies used in traditional lateral logging tools.

Borehole Corrections for a Thick Resistivity Probe

The electrical resistivity contrast between the borehole fluid and the surrounding rock can be very large during borehole logging in crystalline rock. In resistivity logging we are in general interested in acquiring information about the true resistivity of the rock. The fluid will cause an unwanted deflection of the measured apparent resistivity from the sought rock resistivity. The nonconducting probe and its finite dimensions will also affect the measurements. By assuming homogeneous rock and concentric geometry, the Laplace equation has been solved for a thick resistivity probe with normal electrode configuration. The resulting cosine-integral can be calculated numerically with the digital filter method. The corresponding solution for other types of electrode configurations can be found by superposition of results for the normal configuration. The inverse solution that is needed to correct the data is found by fitting calculated values in a least-squares sense to a low-order polynomial. The correction method has been tested on data from a deep hole in granitic rock in south-eastern Sweden. Significant variations in both borehole diameter and fluid resistivity are present in the hole. The assumptions of homogeneous rock and concentric geometry were not valid for the data. In spite of this it was possible to correct the data in a proper way. The resulting estimates of the rock resistivity were about the same for both the normal and the lateral logs. Also, no significant level shifts appeared in the corrected data where there was an abrupt change in borehole diameter. The large volume bulk resistivity of the rock mass was estimated from the corrected data and was found to be in accordance with estimates from ground-based geophysics. By supporting the logging data with petrophysical measurements on core samples it was possible to get reasonable estimates of the rock porosity along the borehole.

Joint inversion of induction/lateral/normal logs, case studies at Shenli field site, China

The behavior of local convergence and nonunique solutions in electric-logging inversion problems make logging interpretation difficult. These negative effects are improved by joint inversion of induction- and galvanic-logging measurements. A two-dimensional joint inversion algorithm is suggested for the simultaneous estimation of formation resistivity, invasion depth and invasion-zone resistivity from field data containing a combination of induction array, lateral and normal devices. Compared with single-log inversion of lateral and normal logs, the joint inversion not only improves the unfavorable local convergence of single inversion, but also constrains the range of possible solutions. Even if the initial guess values vary within a wide region, the joint inversion is fast to converge close to true values; it weakens the dependence of inversion results on initial guesses. In addition, these nonunique solutions are constrained in a limited domain by the present joint inversion technique, thus, the inconsistent interpretations that are usually caused by traditional single-log approach can be avoided. Case studies also illustrate that the present joint inversion of induction/lateral/normal logs provides a reasonable and efficient algorithm that allows for improving the accuracy of the results, enhancing the reliability of formation parameter estimation, and in most cases reducing the uncertainty of hydrocarbon saturation.