No abstract

Although papers comparing some standard functions with saturation models have been published, no consistent review exists comparing the performance of most of the universal saturation-height function quantitatively. The universal SHF is fast and straightforward, but robust enough to account for limited data and while another full data acquisition and advanced analysis are in progress (partially obtained). The method can help the subsurface team in understanding the water saturation nature in quick turnaround time before the completion of ongoing volumetrics estimation. Two best practices of this workflow are rapid and robust. The paper reviews three of the universal saturation-height methods, namely those proposed by Choo, Kyi-Ramli, and K-Function. The comparisons between modelled and measured capillary pressure measurements over the most common functions and through different reservoirs are discussed. The advantages and drawbacks of each method are highlighted. Each technique is compared by investigating how accurately they model the saturation-height profiles of several wells from Offshore Malaysia. The work was carried out to independently assess which equations should be tested first during saturation-height studies. The differences for each capillary pressure between the water saturations estimated using the equations and those measured on the samples are examined in both graphic and quantitative terms. The results of this study show that Choo (2010) model is one of the better performing saturation-height functions. However, the best results are achieved using this function, but this method is also the most challenging to execute in petrophysical and static modelling software. Of the conventional equation-based approaches, the K-Function model appears to have the most utility and are recommended as first choice saturation-height models to test. It only has two inputs for the modelling comprising of RQI and HAFWL. This study continues the extended concepts of Adams (2016) and Harrison (2001) to describe quantitative comparisons between modelled and measured capillary pressure measurements over the functions and through different reservoirs. The review presented could not include all possible equations, but shows which of the most frequently cited functions, is likely to be of utility. Areas for future improvement are also highlighted.

Pressure analysis is concerned with the study of systematic variations of reservoir pore pressure with depth. The most common interpretation for pressure analysis is pressure-depth plot analysis, but other techniques that magnify understated pressure differences are also available. The measurement of formation pressure is of immense value in quantitative evaluation and prospect risk. Once the pressure data has been acquired, we need to understand how to interpret the data received because reservoir pressure data has numerous applications and misinterpreting it could make the results misleading. At equilibrium state (i.e. there are no net forces and no acceleration), a fluid in the system is called hydrostatic equilibrium. Hydrostatic pressure increases with depth measured from the surface due to the increasing weight of fluid exerting downward force from above. The traditional pressure evaluation is usually done in conventional unit such as psi, kPa, psi/feet, psi/m, kPa/m, ppg. The current work will introduce the concepts and definitions of formation pressure evaluation using Pressure Index (PI) with the unit g/cc. For better understanding of the application of PI, some reservoir studies are also discussed in this paper.

Pressure analysis is concerned with the study of systematic variations of reservoir pore pressure with depth. The most common interpretation for pressure analysis is pressure-depth plot analysis, but other techniques that magnify understated pressure differences are also available. Formation pressure measurement is of immense value in quantitative evaluation and risking of prospects. Once the pressure data has been acquired, we need to understand how to interpret the data received because reservoir pressure data has numerous applications and interpreting it wrongly could make the results misleading. At equilibrium state (i.e. there are no net forces, and no acceleration), a fluid in the system is called hydrostatic equilibrium. Hydrostatic pressure increases with depth measured from the surface due to the increasing weight of fluid exerting downward force from above. The traditional pressure evaluation is usually done in conventional unit such as psi, kPa, psi/feet, psi/m, kPa/m, ppg. The current work will introduce the concepts and definitions of formation pressure evaluation using Pressure Index (PI) with the unit g/cc. For better understanding of the application of PI, some reservoir studies are also discussed in this paper.

The purpose of this paper is to design a saturation height function which can overcome the measurement insufficiency and can also be applied to the reservoir models where core measurements are not available at all for all kind of siliciclastic reservoirs. This paper adopts a quantitative approach. The data is collected from the integration of core and log data. This approach is based on the assumption that sandstone reservoirs having similar Rock Quality Index (RQI), has similar capillary pressure behavior as regards water saturation. Universal capillary pressure curves were generated from 22 core plugs in Malaysia, using actual core data. Empirical relations between curve fitting parameters and core plug RQI values were developed. The universal capillary pressure curves were then used in other wells to calculate water saturation which has no core data. For those wells, the pseudo RQI values were calculated using the porosity and permeability derived from the log. A water saturation function was derived, as a function of RQI and HAFWL, with these pseudo RQI values and height above the Free Water Level. The results of this study portray that saturation modelled through this saturation height function matched very well with resistivity derived saturation. Water saturation resulting from generalized capillary curves was contrasted in wells without core data to that computed from resistivity logs. These water saturation results were found to be more realistic than those calculated purely from resistivity logs. The results confirmed the assumption that the universal capillary pressure curves can be used without core data to predict water saturation in wells. A well that has intercepted a hydrocarbon accumulation effectively represents a massive core sample of the reservoir. It is now possible to calculate the saturation reliably in any well. RQI is known over the entire hydrocarbon column. At the saturation anywhere in a reservoir can be determined, and the FWL known or estimated with reasonable certainty. It is in principle viable to evaluate Sw directly based on the drainage capillary theory. This study provides an insight into the universal saturation height function as a basic formulation in designing, developing, and appropriate strategies to model water saturation. This study not only helps subsurface study team in modelling water saturation, but it also offers new insights concerning the ability and capability of the strong direct relationship among rock quality index, height above free water level, and water saturation. This study uses an extended concept of Cuddy et al. (1993) to describe how water saturation varies with height above the free water level (FWL). Cuddy proposed the relationship of bulk Volume of Water vs Height above the FWL to derive water saturation. This approach requires conversion from BVW to SW. The proposed function, called K-function does not require the conversion.