Cased-Hole Reservoir Saturation Monitoring in Mixed Salinity Environments - A 
New Integrated Approach

Ma, Sai; Al-Hajari, A.; Berberian, Garabed; Ramamoorthy, Raghu

doi:10.2523/92426-ms

Cited by 7 publications

(9 citation statements)

References 5 publications

(5 reference statements)

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“…Hence, a strong correlation represents an independent confirmation of wettability variation. Ma et al (2005) show that the resistivity index recorded during the drainage and imbibition cycles in carbonates can follow different paths. The cores under study were allowed to age at reservoir temperature and pressure at the end of the drainage cycle while saturated with reservoir crude.…”

Section: Wettability Estimates From Logsmentioning

confidence: 93%

Integration of Dielectric Dispersion and 3D NMR Characterizes the Texture and Wettability of a Cretaceous Carbonate Reservoir

et al. 2013

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Knowledge of rock texture and wettability are vital for the static and dynamic description of carbonate reservoirs. Conventional log measurements are limited in their applicability for the quantitative assessment of these attributes. Rapid variations of texture in carbonates diminishes the usefulness of core measurements on samples of limited size. Obtaining representative relative permeability by restoring core to native reservoir conditions, especially the original wettability state, is also very challenging.The dielectric response of clean carbonate rocks exhibit characteristic frequency dispersion patterns which depend on their texture and wettability. Dielectric measurements with multiple frequencies have become available enabling us to extract this information by inverting the tool data using a dispersive petrophysical model.The dielectric response is primarily sensitive to water, and provides a measure of the water phase tortuosity, which is a combination of texture and wettability, captured in the Archie's exponents m and n. Previous work has demonstrated the estimation of m from pore size distribution obtained from NMR data using an effective medium model. Formation Resistivity Factor data from core is presented to validate the model-derived m. In this work we propose a way to combine the cementation exponent so derived with the textural answers from the dielectric measurement to make a wettability estimate. We also assess the wettability from 3D NMR stations, using the increase in relaxation of oil manifested as shortening of the oil T 2 signal due to partial wetting of the oil phase. The methods are illustrated on a dataset from a Cretaceous carbonate, onshore Abu Dhabi. The interval surveyed in the subject well straddles an oil/water contact (OWC). The n exponent value derived by the method shows that the rock above the OWC is oil-wet in varying degrees. The inference on wettability state from the NMR data further supports the conclusions.

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Section: Wettability Estimates From Logsmentioning

confidence: 93%

Integration of Dielectric Dispersion and 3D NMR Characterizes the Texture and Wettability of a Cretaceous Carbonate Reservoir

et al. 2013

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“…In the case of reservoirs under water injection this might not always be true, since the saturation exponent "n" can vary depending on whether the rocks are in drainage (oil displacing water) or imbibition (water displacing oil) state (Ma et al, 2005). For carbonates it is also known that the cementation factor "m" is related to rock texture (presence of isolated, moldic porosity; fractures, etc.…”

Section: Archie Equation Parametersmentioning

confidence: 99%

“…A methodology integrating data from water samples collected at surface or at the bottom of the hole was proposed by Ma et al, 2005, to calibrate a pseudo formation water salinity profile derived from the C/O logs (using Cl and H yields from the capture spectra). The calibrated formation water salinity can thereby be used to compute Sw more accurately from resistivity.…”

Section: Introductionmentioning

confidence: 99%

“…In Eyvazzadeh et al, 2005, examples illustrate how the error in Sw computed from C/O increases rapidly when porosity goes below 15 p.u. In Ma et al, 2005, C/O logs are not recommended below 15 p.u. Although there is no clear consensus in the industry and results may vary depending on the borehole environment, tool design and number of recorded/stacked passes, for practical purposes, C/O logs are usually limited to above the 10 p.u.…”

Section: Introductionmentioning

confidence: 99%

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Combining Resistivity and Capture Sigma Logs for Formation Evaluation in Unknown Water Salinity: A Case Study in a Mature Carbonate Field

et al. 2010

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Formation evaluation in unknown water salinity can be done by solving simultaneously for Sw and Rw from the logs of resistivity and sigma. This has not been used extensively in the past because the logs are often acquired on wireline at various times, leading to unknown invasion effects that complicate the integration of the deep-reading resistivity and the shallow-reading sigma logs. We will show that when the two measurements are free from invasion effect -and other interpretation parameters, such as porosity, Archie m and n, etc., are reasonably known -the technique works well and gives reliable Sw and Rw answers.Both numerical and graphical solutions are presented. The numerical technique uses a minimization routine to solve for a salinity value that is consistent with Sw calculated from resistivity and from sigma. The salient point of the paper is the graphical technique that provides better insights into petrophysics than a set of equations. It uses an overlay of equi-saturation and equi-salinity lines superimposed on the crossplot of sigma versus resistivity data. The overlay dynamically changes as porosity, lithology, hydrocarbon type, temperature, and other parameters vary with depth. The graphical technique has several applications. For the interpretation, it is used to estimate Sw and salinity, and to identify zones of changing properties. For quality control, it is used to validate the input data. For processing, it is used to select parameters and analyze their sensitivities to the results. For job planning, it is used to validate (or invalidate) the application from input values of resistivity and sigma. The graphical technique provides a valuable aid to the petrophysicist and gives an independent verification of the numerical solution.The proposed technique is illustrated with wireline induction and sigma logs acquired in several wells in a mature Middle East carbonate field. The wells under study are completed in open hole and are flowed during logging to ensure that both resistivity and sigma logs are free from invasion effect. The results of the resistivity-sigma technique compare very favorably with those of carbon-oxygen (C/O) logging. Moreover, production logging data confirmed the results and showed that the resistivity-sigma technique provides more robust answers than C/O in low-porosity formations (below 15 p.u.).

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“…pulsed neutron (PN) and resistivity logs, have very shallow depth of investigation (ranging from a few centimeters for PN logs to a maximum of about 3 m for the resistivity logs 3 and are limited to near well bore measurements. Therefore, they cannot be used effectively for flood-front monitoring at the inter-well scale.…”

Section: Introductionmentioning

confidence: 99%

Crosswell Electromagnetic Resistivity Tomography: Pushing the Limits

et al. 2007

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe cross-well electromagnetic (EM) resistivity method is emerging as one of the technologies that can be deployed for very deep reservoir surveillance/monitoring measurements. It has the potential to provide fluid distribution mapping at interwell scale, and thus can be used for identification of bypassed hydrocarbon, monitoring of macroscopic sweep efficiency, planning infill drilling and improving effectiveness of reservoir simulation.A cross-well EM trial is being conducted in an Upper Jurassic carbonate reservoir in Saudi Arabia to monitor the flood-front and fluid distribution with a well separation at the upper limit of the operating envelope allowed by this technology. For best results, current technology limits the maximum distance between wells to circa 1000 m for open-hole to open-hole and 300 m for cased-hole to cased-hole. Extensive pre-job forward modeling was carried out to investigate the feasibility of obtaining useful results from the measurements with such large inter-well spacing. Several scenarios of flood-front movement, such as edge water due to super-K or fracture swarms, bottom water encroachment, coning and cusping, etc., were modeled.The modeling results were encouraging and many of the anticipated subsurface scenarios were successfully detected.

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Cased-Hole Reservoir Saturation Monitoring in Mixed Salinity Environments - A New Integrated Approach

Abstract: TX 75083-3836, U.S.A., fax 01-972-952-9435. Near wellbore effects Effect on shallow nuclear logging Deviated wells Acid effect Effect on Σ Lithology

Cited by 7 publications

References 5 publications

Integration of Dielectric Dispersion and 3D NMR Characterizes the Texture and Wettability of a Cretaceous Carbonate Reservoir

Integration of Dielectric Dispersion and 3D NMR Characterizes the Texture and Wettability of a Cretaceous Carbonate Reservoir

Combining Resistivity and Capture Sigma Logs for Formation Evaluation in Unknown Water Salinity: A Case Study in a Mature Carbonate Field

Crosswell Electromagnetic Resistivity Tomography: Pushing the Limits

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