It's been long years of trials worldwide to find the relation between permeability and any other reservoir property or log and/or relation with combination of them. There have been even neural network, fuzzy logic and equation solver software modules used to enable extracting and finding probable sophisticated equation for permeability determination from log data, in a way replicating Archie's Equation for water saturation determination, however; it's important to keep in mind that core analysis were unable to provide proper reservoir water saturation due to coring operation deficiency in preserving core fluid from the time of coring until reaching surface and labs unless highly cost pressure coring was conducted. While core plug permeability measurements provide solid reference of permeability; in the other hand, if water saturation determination from logs is wrong no one can easily challenge it and proves opposite. Here, in this paper a new analysis approach is innovated and detailed, as the analysis did not look for one relationship between permeability across all geological layers and specific log data like previous approaches; instead, the new approach is finding multi relations between permeability variations across each layer and several log data types until finding the suitable log or logs that are providing adequate relation. As we found that each reservoir layer permeability range responds to different log data types more sound and obvious than other log data types, in a way reflecting the domination reasons for permeability ranges whether they are due to fracture or matrix or any other structural, stratigraphic, deposition or digenetic effects. This technique is utilized successfully in three different reservoirs; fractured limestone, non-fractured heterogeneous limestone and dolomitized-limestone.

Accurate water saturation estimation in thin carbonate reservoirs is one of the major formation evaluation challenges in horizontal wells. This is mainly due to the strong shoulder bed effect of thick dense sections on the resistivity logs recorded in thin porous reservoir layers, particularly in horizontal wells.The performed work implies correction of the high resistivity log data acquired while drilling horizontal well sections by means of resistivity modeling. This has been achieved by building a forward model for the resistivity data acquired in the deviated section of the overlying reservoirs in water injector wells, where the porous section is thick and the shoulder bed effect is minimal. The resistivity model construction is based on the relationship of the deep and shallow Laterolog resistivity to the neutron porosity log responses measured in the thick reservoir sections. The established model equations are used to construct deep and shallow resistivity logs in the horizontal sections of thin reservoirs by resistivity inversion using the neutron porosity log data.Several well data sets have been tested and the results were complimented by test data, formation tester fluid sample analysis, Dean Stark measurements and core data. The results obtained confirmed that the resistivity inversion technique is applicable to compute water saturation in both the flushed zone (Sxo) and the un-invaded zone (Sw) for horizontal well sections drilled across carbonate reservoirs. The application of the inversion process allows generating resistivity log responses corrected for the tight shoulder bed effects, and providing more accurate water saturation estimation.

Oil industry's basic tool for in-situ determination of hydrocarbon saturation is resistivity log. Since 1942, Archie's empirical relations have been used to calculate oil (and water) saturations, which are vital for field development. Sw (Water Saturation) and So (Oil Saturation) values are needed in several phases of reservoir life; exploration, development, monitoring, management and long term plans. In one of major Abu Dhabi offshore fields, a study to develop optimum methodology for determining Archie parameters that represent the corresponding rock properties is initiated. This is to replace the use of one constant value of by variable curve that respond to different rock properties. In this paper, Archie's equation parameters determination techniques have been reviewed and analyzed. Cost effective, high confidence rock & Log type integration methodology were innovated to determine variable values of two parameters; Cementation and Saturation Exponent. Before this study, Special Core Analysis measurements were the main techniques to get the two parameters. In this study, thorough investigation on utilizing Neutron, Density, Resistivity & Dielectric logging measurements as replacement of core analysis have showed for valuable opportunity to establish new water saturation log interpretation standards in carbonate rock.

Sourceless porosity estimation has become more attractive because of evolving government regulatory and HSE requirements. The use of wireline nuclear sensors and their HSE procedures have a 50-year history, while nuclear sensors for logging while drilling share the last 20 of those years. Recently, the potential of using non-nuclear methods for porosity estimation has been explored in an offshore Abu Dhabi carbonate sequence. This paper presents a case study of nuclear magnetic resonance (NMR) logs while drilling, in comparison to conventional density and neutron logs using radioactive chemical sources. NMR T1 porosities were also compared to laboratory core results. Two approaches are investigated: Estimated hydrogen-index correction to NMR moveable-fluid volume using core-normalized porosities.An insight into an integrated NMR-acoustic approach, using the two sensor measurements to derive a corrected porosity. A workflow is proposed for optimized job planning, operational procedures, data-acquisition parameters, and interpretation techniques. Permeability estimation with NMR is discussed, and a selection of methods are considered and contrasted to laboratory core permeability and wireline formation-tester results. This paper explores the potential for sourceless porosity measurements through NMR and acoustic/NMR measurements in an offshore Abu Dhabi carbonate sequence in compliance with the HSE standards and government regulations, where the need for reconsidering reservoir characterization through sourceless porosity options will continue to grow.

In one of the biggest carbonate reservoir in offshore Abu Dhabi that has been producing oil for more than 40 years, oil potential evaluation is affected by many uncertainties as evaluated via pulsed neutron technology across perforated intervals.The Acid used to stimulate the wells after workovers affect the responses of the pulsed neutron logs. Efforts have been exerted to eliminate this effect. Observations from this field showed that the acid life cycle in the formation can be extracted by comparing and correlating several pulsed neutron sigma logs that are acquired over the years across the same perforated intervals.It has been noticeable that one of the most influential parameters in removing or eliminating acid existance in reservoir rock is water production, otherwise acid effect on pulse neutron sigma log interpretation remains, resulting in calculating high water saturation across dry oil producing zones.Understanding this acid effect life cycle helped understanding reservoir performance and reducing uncertainty of pulse neutron sigma interpretation. This paper is showing these observations in our field and is detailing acid effect modeling on pulsed neutron log responses.