Conventional Logging Tools Research Articles

Petrophysical Evaluation of the Zubair Formation’s Main Pay Zone Using Conventional and NMR Log Data: Insights from the North Rumaila Field, Southern Iraq

This study investigates the calculation of petrophysical properties using both conventional logging tools and Nuclear Magnetic Resonance logs for the main pay zone of the Zubair Formation, Recognized as one of the most significant hydrocarbon-producing formations in the North Rumaila Field, located in southern Iraq, the main pay zone is categorized into three permeable units (AB, DJ, and LN) and two impermeable isolated zones (C and K) based on log responses. The petrophysical analysis of these zones indicates that the shale volume increases toward the northern part of the field due to the depositional environment. Effective porosity values across these zones range from fair to good; however, some wells in the AB layer exhibit excellent porosity, notably wells X-7, X-62, X-83, and X-110. Additionally, hydrocarbon saturation levels remain consistently high in the AB and DJ layers, whereas certain wells in the LN layer display lower saturation values, particularly wells X-85, X-78, X-63, X-110, X-84, X-19, and X-115. Furthermore, permeability values were calculated using the KSDR equation based on Nuclear Magnetic Resonance logs that span from good to very good, except well X-115, demonstrating excellent permeability in the AB layer.

Unreliable determination of in situ stress orientation by cross multipole array acoustic logging in fractured shale reservoirs

Abstract With the development of shale gas exploration in China, the use of conventional logging tools has been introduced, and cross multipole array acoustic logging tools have gradually been used to determine the stress orientation in shale. The direction of fast shear waves (FSWs) is generally parallel to the horizontal maximum principal compression stress (SHmax). However, the azimuth of FSWs is found to be parallel to the main strike (but not to the SHmax) direction of structural fractures in shale reservoirs. Outcrop and image logging data indicate that the natural fractures in this area strike NE‒SW. If the shear wave anisotropy is caused by only the stress around the borehole and the FSWs are known to be NE‒SW, SHmaxshould be parallel to NE‒SW; however, according to statistics of land movement in adjacent areas, anelastic strain recovery, earthquake focal mechanism, borehole breakouts, hydraulic fracturing data, deviated well data, and drilling‐induced fracture data in local regions, SHmaxis oriented in the NW‒SE direction, and the directions of FSWs are generally parallel to the structural fracture direction. This contradiction indicates that the development of structural fractures may affect the orientation of FSWs. Therefore, it is not reliable to use XMAC (Cross‐Multipole Array Acoustilog) logging only to determine the direction of in situ stress in fractured shale reservoirs. In addition, the direction of the FSWs in the middle of thick mudstones is NW‒SE, which may represent accurate information about the in situ stress direction.

Carbonate fractures from conventional well log data, Kometan Formation, Northern Iraq case study

Carbonate fractures from conventional well log data, Kometan Formation, Northern Iraq case study

A new integrated approach to resolve the saturation profile using high-resolution facies in heterogenous reservoirs

A new integrated approach to resolve the saturation profile using high-resolution facies in heterogenous reservoirs

Miniaturized Casing Collar Locator for Small Downhole Robots

Despite advances in robotics for many harsh environments, the downhole environment is rarely accessed by robots. Small, autonomous robots for logging oil and gas wells potentially offer significant cost savings over conventional wireline logging tools, but there are some major technical challenges to overcome. Among these is navigation or how the robot can know its own position along the well. Oil and gas wells are lined with steel casing, made up of 40-ft-long pipe joints held together by threaded collars. The collar locations could potentially be used as features for navigation, but conventional magnetic casing collar locator (CCL) sensors are large and must be mechanically stabilized within the casing. This letter investigates the design of CCLs for small, untethered robots with limited energy resources.

An enhanced ANFIS based approach for estimating petrophysical properties of thinly laminated reservoirs in absence of core data

Obtaining reliable petrophysical estimation of the thinly laminated reservoirs is a major challenge due to the convoluting effect of laminations on the conventional logging tools that jeopardizes the accuracy of the interpretations and hence poses major risks to the resource evaluation and field development planning. Many existing parametric or non-parametric correlations fail to provide reliable estimations and therefore domain expert knowledge is critical in the studies pertaining to thinly laminated reservoirs. We present a two-step approach based on neuro-fuzzy inference system (FIS), and harnessing the available expert knowledge for proper depositional environment (DE) analogues that determine the ranges of the parameters for the estimation exercise. Application of the method to the data from different DEs shows satisfying outcome. The use of a FIS to mine for proper DE that represents the thinly laminated sand reservoir at hand, prior to use of ANFIS, sets the proposed approach apart from other available research based on conventional applications of non-parametric regression methods. The proposed approach provides a pragmatic tool for estimating the properties of thinly laminated sands when no core data is available. It, therefore, greatly improves the modeling of laminated reservoirs, and therefore helps mitigate the risks associated with the field development.

Estimation of Water Saturation in Shale Formation Using In Situ Multifrequency Dielectric Permittivity

Estimating water saturation via conventional logging tool such as resistivity cannot provide an accurate solution in a formation with low conductivity water and tight porosity. As an alternative, we employed a dielectric permittivity, which makes it easy to differentiate the water from the other fluids in pore structures. A multichannel frequency dielectric logging tool is used for measuring in situ permittivity. To simulate a dielectric permittivity, we used two analytic models: Lichtenecker-Rother (LR) and Stroud-Milton-De (SMD) models. The key goal of this research is to propose a workflow to evaluate an equivalent Archie’s parameter which can generate the same dielectric logging tool responses with core measurement results using a given analytic models. According to the results of the LR model curve-fitting, the estimated Archie’s parameter shows inversely proportional relationship with clay volumes. The estimated Archie’s parameter from the SMD model is sensitive to the lower frequency channels of the multifrequency dielectric logging tool. Nevertheless, utilizing the response of the dielectric logging tool in the frequency range, where interfacial polarization effect does not exist, can provide an alternative to estimate water saturation in shale formations with relatively less conductive waters.

Synthesizing Nuclear Magnetic Resonance (NMR) Outputs for Clastic Rocks Using Machine Learning Methods, Examples from North West Shelf and Perth Basin, Western Australia

A nuclear magnetic resonance (NMR) logging tool can provide important rock and fluid properties that are necessary for a reliable reservoir evaluation. Pore size distribution based on T2 relaxation time and resulting permeability are among those parameters that cannot be provided by conventional logging tools. For wells drilled before the 1990s and for many recent wells there is no NMR data available due to the tool availability and the logging cost, respectively. This study used a large database of combinable magnetic resonance (CMR) to assess the performance of several well-known machine learning (ML) methods to generate some of the NMR tool’s outputs for clastic rocks using typical well-logs as inputs. NMR tool’s outputs, such as clay bound water (CBW), irreducible pore fluid (known as bulk volume irreducible, BVI), producible fluid (known as the free fluid index, FFI), logarithmic mean of T2 relaxation time (T2LM), irreducible water saturation (Swirr), and permeability from Coates and SDR models were generated in this study. The well logs were collected from 14 wells of Western Australia (WA) within 3 offshore basins. About 80% of the data points were used for training and validation purposes and 20% of the whole data was kept as a blind set with no involvement in the training process to check the validity of the ML methods. The comparison of results shows that the Adaptive Boosting, known as AdaBoost model, has given the most impressive performance to predict CBW, FFI, permeability, T2LM, and SWirr for the blind set with R2 more than 0.9. The accuracy of the ML model for the blind dataset suggests that the approach can be used to generate NMR tool outputs with high accuracy.

Low-Resistivity/Low-Contrast Reservoirs Increase Production in Offshore Brownfield

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 202331, “Unlocking the Hidden Oil: How Low-Resistivity, Low‑Contrast Reservoirs Contributed to 800 BOPD of Production in a 30‑Year‑Old Offshore Brownfield,” by Su Li Tham, SPE, Kwang Chian Chiew, and Hamed Hassani, Petronas, et al. The paper has not been peer reviewed. Production-enhancement opportunities in 30-year-old Field D in Balingian province, offshore Sarawak, are dwindling. An in-house evaluation tool, resolution enhanced modeling (REM), was developed to evaluate and characterize thin beds or laminations. These low-resistivity/low-contrast (LR/LC) sands are commonly bypassed because conventional logging tools cannot resolve their true parametric values and the apparent log responses across these zones appeared as shaly sand. By running REM across these intervals, the properties of the thin sands could be characterized properly, improving the net pay and economics of perforating and producing these reservoirs. Introduction The major reservoirs of Field D were deposited in a fluvial environment, resulting in channel sands, and are mainly under solution gas drive with weak aquifer and large gas-cap drive. The major sands generally are well-developed, including the implementation of water injection as a secondary recovery method in 2016 and perforation of remaining behind-casing opportunities across the field. As the field enters its later life, attention has been shifted to minor reservoirs in a final effort to extract remaining oil from wells before abandonment. In the case of Field D, the focus is on the LR/LC reservoirs (Fig. 1). These reservoirs mostly are shaly sands and are localized because of their depositional environment of mouth bars and crevasses. There are exceptions, however, as observed in Well A3-S and Well C6, where the reservoirs are clean sands with a thickness of 5–10 ft; these wells likely have penetrated the center of a mouth bar or crevasse. These LR/LC plays can be detected only by high-resolution logs or core photography. Consequently, LR/LC reservoirs are often overlooked because their properties and hydrocarbon saturation are underestimated, thereby placing them below the cutoff as pay zones. Thus, reservoir characterization and subsequent estimation of reserves remain a challenge in maturing LR/LC perforation proposals.

Evaluation of azimuth cement bond quality based on the arcuate phased array acoustic receiver station

Evaluation of azimuth cement bond quality based on the arcuate phased array acoustic receiver station

Estimating reservoir permeability with borehole radar

In oil drilling, mud filtrate penetrates into porous formations and alters the compositions and properties of the pore fluids. This disturbs the logging signals and brings errors to reservoir evaluation. Drilling and logging engineers therefore deem mud invasion as undesired and attempt to eliminate its adverse effects. However, the mud-contaminated formation carries valuable information, notably with regard to its hydraulic properties. Typically, the invasion depth critically depends on the formation porosity and permeability. Therefore, if adequately characterized, mud invasion effects could be used for reservoir evaluation. To pursue this objective, we have applied borehole radar to measure mud invasion depth considering its high radial spatial resolution compared with conventional logging tools, which then allows us to estimate the reservoir permeability based on the acquired invasion depth. We investigate the feasibility of this strategy numerically through coupled electromagnetic and fluid modeling in an oil-bearing layer drilled using freshwater-based mud. Time-lapse logging is simulated to extract the signals reflected from the invasion front, and a dual-offset downhole antenna mode enables time-to-depth conversion to determine the invasion depth. Based on drilling, coring, and logging data, a quantitative interpretation chart is established, mapping the porosity, permeability, and initial water saturation into the invasion depth. The estimated permeability is in a good agreement with the actual formation permeability. Our results therefore suggest that borehole radar has significant potential to estimate permeability through mud invasion effects.

Applications of real-time chemical stratigraphy in support of the safe drilling of HPHT wells: examples from the Shearwater Field, Central North Sea, UK

X-ray fluorescence (XRF) data from a series of high-pressure–high-temperature (HPHT) wells drilled in the Shearwater Field, UK Continental Shelf (UKCS) are presented. These data comprise a total of 789 samples across a series of eight study wells. Chemical stratigraphy was utilized in conjunction with other geological data (i.e. well logs, ditch cutting descriptions and biostratigraphic analyses) to aid real-time stratigraphic placement. Systematic changes in geochemical composition were identified and used to build a chemostratigraphic zonation to aid delineation of lithostratigraphic boundaries. The application of chemical stratigraphy provided a valuable source of data, particularly through critical ‘drill-in-liner’ sections that are devoid of conventional logging while drilling (LWD) data. The identification of key geochemical zones and provision of a synthetic gamma-ray (Synth GR) profile were utilized in the placement of key casing points and identification of challenging top reservoir picks (Fulmar Formation). These data also served as a backup during LWD tool failure resulting from excessive temperatures. The successive addition of geochemical data accumulated with each well-site exercise permitted continued refinement of the zonation framework, with derived Synth GR profiles exhibiting an extremely close relationship with subsequent wireline logs. Chemical stratigraphic data are shown to be robust and repeatable within the Shearwater Field, enabling close stratigraphic control through critical sections, whilst also providing a low-cost backup in the event of conventional logging tool failures.

Neutron transport correction and density calculation in the neutron-gamma density logging

Neutron transport correction and density calculation in the neutron-gamma density logging

A general experimental system for the development of acoustic logging tools.

Laboratory testing is a pre-requisite for the practical application of new methods and techniques, and it is crucial in the research and development of acoustic well-logging tools. Various tools have been developed based on different acoustic logging theories and methods. Thus, these tools are equipped with different acoustic sonde structures. To meet the test requirements of different tools in a laboratory environment, we designed a general experimental system that includes hardware platform, software platform, and model wells according to the common structure of actual logging tools. Similar to the internal electrical structure of downhole tools, the hardware platform consists of several main parts, such as power supply, control and telemetering, acoustic emission, and data acquisition. The functions of this hardware platform include controlling the working sequence of the experiment, exciting the transmitter sonde, and collecting the acoustic signals received by the receiver sonde. The software platform installed in the host computer provides a human-computer interface for the experimental system to complete the data transmission between the host computer and the hardware platform, store measured data, and process the data in real time. The model wells approximate the actual engineering environment and stratum condition for system testing. A series of practical laboratory experiments is conducted in the model wells by using this experimental system. The process proves that the hardware and software of the experimental system can work in coordination, and the experimental system meets the basic testing requirements of conventional acoustic logging tools.

Ungani Oil Field, Canning Basin - Evaluation of a Dolomite Reservoir

Core supported study of the heterogeneous Ungani dolomite reservoir architecture is driving development drilling and upgrades to field resource estimates. Vuggy connected and macro non-connected pore space was directly measured over a 70m continuous core using 3D structural analysis of CT-scans. Plug density measurements indicate non-connected or sub-140 micron resolution contribution of around 1% to 2.5% (pu) for the tight matrix, but all remaining porosity potentially contributes to oil production. The high resolution core porosity data is vertically repositioned and upscaled to calibrate neutron-density and sonic petrophysically derived porosities which are inadequate to resolve productive zones using conventional reservoir cut-offs. Conditioned resistivity image data correlated exceptionally with directly measured connected porosities. Reservoir properties were extrapolated to all wells across the Ungani field giving field net/gross estimates of up to 63% and porosities over 30% pu in some vuggy and brecciaed zones. The heterogeneity and prolific nature of the uppermost 17m of reservoir had not been previously recognised due to poor log data coverage and access at the casing points. Recent re-analysis of this section at Ungani-3 with Chemostrat ICP-OES-MS analysis of ditch cuttings was instrumental in proposing additional drilling to re-target this zone. Mineralogy analysis is used to calculate rock grain densities and help calibrate neutron-density derived porosity logs over the Ungani field. Up-scaled core porosity correlates well with density and sonic porosity logs. Resistivity logs adjusted for minerology can also be used to predict porosity and support the use of resistivity image logs to identify vuggy zones and estimate porosity at a higher resolution than conventional logging tools. A field static model was populated with three facies distributed over vertical zones according to the distribution encountered in the core porosity analysis and well logs, and iteratively matched to the dynamic pressure data and field production history which exhibits field scale multi-Darcy horizontal permeability and protection from vertical water cut. Further drilling and downhole artificial lift is planned to extend field production rates to 3000 bbls/day. Increased confidence in this regionally developed reservoir is supporting further exploration of undrilled prospects in this immature and under-explored trend

Metaheuristic optimization approaches to predict shear-wave velocity from conventional well logs in sandstone and carbonate case studies

Seismic wave velocities, along with petrophysical data, provide valuable information during the exploration and development stages of oil and gas fields. The compressional-wave velocity (VP ) is acquired using conventional acoustic logging tools in many drilled wells. But the shear-wave velocity (VS ) is recorded using advanced logging tools only in a limited number of wells, mainly because of the high operational costs. In addition, laboratory measurements of seismic velocities on core samples are expensive and time consuming. So, alternative methods are often used to estimate VS . Heretofore, several empirical correlations that predict VS by using well logging measurements and petrophysical data such as VP , porosity and density are proposed. However, these empirical relations can only be used in limited cases. The use of intelligent systems and optimization algorithms are inexpensive, fast and efficient approaches for predicting VS. In this study, in addition to the widely used Greenberg–Castagna empirical method, we implement three relatively recently developed metaheuristic algorithms to construct linear and nonlinear models for predicting VS : teaching–learning based optimization, imperialist competitive and artificial bee colony algorithms. We demonstrate the applicability and performance of these algorithms to predict Vs using conventional well logs in two field data examples, a sandstone formation from an offshore oil field and a carbonate formation from an onshore oil field. We compared the estimated VS using each of the employed metaheuristic approaches with observed VS and also with those predicted by Greenberg–Castagna relations. The results indicate that, for both sandstone and carbonate case studies, all three implemented metaheuristic algorithms are more efficient and reliable than the empirical correlation to predict VS . The results also demonstrate that in both sandstone and carbonate case studies, the performance of an artificial bee colony algorithm in VS prediction is slightly higher than two other alternative employed approaches.

Evaluation of laminated shaly sand sequences in Ahwaz oil field using (via) Thomas Stieber method and conventional petrophysical logs

Evaluation of laminated shaly sand sequences in Ahwaz oil field using (via) Thomas Stieber method and conventional petrophysical logs

Formation evaluation logoff results comparing new generation mining-style logging tools to conventional oil and gas logging tools for application in coalbed methane (CBM) field development

Formation evaluation logoff results comparing new generation mining-style logging tools to conventional oil and gas logging tools for application in coalbed methane (CBM) field development

Identification of fractures in carbonates using sonic imaging logs Example from the central of East European plain

Compared with sandstone, the structure of carbonate rocks is much more complex for its heterogeneity and anisotropy. The Republic of Tatarstan of Russia lies in the central of East European Plain, where oil-gas resource is very rich, and formations are mainly carbonates. In order to detect the underground geology of the region, array acoustic logging tool, micro-electrical scanning tool, and conventional logging tools were applied. We processed and analyzed the array acoustic logging data. The results demonstrated that monopole shear wave attenuation, Stoneley wave attenuation and monopole variable-density waveforms were all sensitive to the boundary where wave impedance contrast was high. The boundary may be a fracture, or a bed interface between shale and limestone in the region. In the micro-electrical scanning images, both the low-angle fracture and the bed interface showed one sine curve. The sine curve of the low-angle fracture was relative rough and the curve width changed with different azimuth, compared with that of the bed interface. The direction of fracture and stress can be obtained by processing cross-dipole waveforms of array acoustic logging data. Micro-electrical scanning tool provided three caliper curves of different azimuth that can determine borehole expanding direction, further getting the stress direction.

Technology Focus: Nanotechnology (February 2013)

Technology Focus Advances in nanotechnology have revolutionized many aspects of medical treatments and electronics, and huge potential exists for similar benefits to be realized in the oil industry. Operators and service companies, in cooperation with academia, are investigating the potential applications of nanotechnology and examining the scope for crossover technologies that have been developed for other industries. The range of applications is enormous and has the potential of enhancing well integrity and productivity along with improving recovery. Much attention is currently being directed toward surface modification using nanomaterials, nanoparticles that can be custom functionalized for specific applications, and improvements in metallurgy and cement used in well completions. With regard to surface modification, nanotechnology has been developed and used that can coat specific parts of the completion or near-wellbore region such that they are more resistant to corrosion or erosion or to the adherence of scale or hydrates. Research is also ongoing into self-healing nanosurfaces that autorepair if damaged, a feature that would be very useful in high-velocity gas completions/flowlines. When it comes to nanoparticles, an enormous range of applications has been and is being developed. Functionalized nanoparticles, whereby the particles are assigned particular attributes, are potentially the most interesting of these. This feature, combined with their size, means that nanoparticles can be transported very easily through porous media. Given these characteristics, potential and actual applications include transport of production chemicals and enhanced-oil-recovery (EOR) enhancers to specific sites with-in the near-wellbore region and reservoir where the chemicals are released at a given temperature, pH, or time. Examples of potential applications currently under investigation include scale inhibitors and surfactants for wettability alteration in nanoenhanced EOR. Swellable nanoparticles are being considered for improving reservoir sweep where injection water would be directed from parts of the reservoir with low oil saturation to those parts with much higher saturation because of selective pore blockage. Nanoparticles can also be functionalized such that they act as nanosensors, something that could be used for reservoir monitoring or surveillance. This crossover technology from the medical industry could be used to provide information on reservoir characteristics deeper in the reservoir than conventional logging tools can probe. The sequence of papers selected is designed to give an indication of the current activities within nanotechnology. This range of activities is enormous, and it will be exciting to see which nanotechnologies break through and become industry accepted. Recommended additional reading at OnePetro: www.onepetro.org. IPTC 15152 Nanotechnology Applications in Oil and Gas Exploration and Production by Sergio Kapusta, Shell, et al. SPE 154827 Application of Nanofluid Technology To Improve Recovery in Oil and Gas Wells by Paul McElfresh, Frac Tech Services International, et al. IPTC 15312 Fluorescent Nanobeads: A New Generation of Easily Detectable Water Tracers by Nicolas Agenet, Total, et al.