Assessment of  Residual Oil Saturation in a Large Carbonate  Reservoir

Pham, Tony; Al-Shahri, Ali

doi:10.2523/68069-ms

Cited by 6 publications

(2 citation statements)

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“…The thus estimated KwKo curve was normalized in terms of its terminal points (pairs (Swc, Krocw) and (1-Sorw, Krwro)). A residual oil saturation value was attributed to each cell in the simulation grid (that is, a Sorw map was constructed), grounded on the correlation with the connate water saturation (Swc) attained through the data obtained from reference (8). This correlation is shown on figure 5; the Sorw was, in average, around 30%.…”

Section: Rock Propertiesmentioning

confidence: 99%

The Role of the Value of Information and Long Horizontal Wells in the Appraisal and Development Studies of a Brazilian Offshore Heavy-Oil Reservoir

Branco

Pinto

Tinoco

et al. 2005

Proceedings of SPE/PS-CIM/CHOA International Thermal Operations and Heavy Oil Symposium

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fax 01-972-952-9435. AbstractRecent exploration efforts in the Campos Basin, offshore Brazil, have resulted into important discoveries of what is known as "offshore heavy oil" (API gravities below 18 and reservoir viscosities above 20 cp). Actually, these accumulations have been known since the beginning of the development of the Basin, in the 80s, but they were never given a chance of development due to the technology challenges involved. The maturation of lighter oil fields, associated with recent technology developments (1,2,3), has boosted the interest for these heavy oil resources set aside for many years. This paper describes the simulation model building process, the difficult task of assigning scarcely sampled rock and fluid properties, the uncertainty study and the use of quality maps for placing the wells. Simulations results have shown the importance of the well footage and its effectiveness in contacting the reservoir rock.

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Section: Rock Propertiesmentioning

confidence: 99%

The Role of the Value of Information and Long Horizontal Wells in the Appraisal and Development Studies of a Brazilian Offshore Heavy-Oil Reservoir

Branco

Pinto

Tinoco

et al. 2005

Proceedings of SPE/PS-CIM/CHOA International Thermal Operations and Heavy Oil Symposium

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“…The reservoir is gravity dominated which provides a bottoms-up sweep mechanism as explained by Pham (2) in a paper discussing the Residual Oil Evaluation in Ghawar Arab-D reservoir. As discussed later in the paper, this depletion mechanism was confirmed by the dual porositypermeability model which was used to evaluate the completion strategy.…”

Section: Geological Settingmentioning

confidence: 99%

Logistic Approach in Using an Array of Reservoir Simulation and Probabilistic Models in Developing a Giant Oil Reservoir with Super-Permeability and Natural Fractures

Pham

Al-Otaibi

Al-Ali

et al. 2002

Proceedings of SPE Annual Technical Conference and Exhibition

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe development of a large oil increment with superpermeability (super-K) layers, and natural fractures such as Haradh Arab-D poses many challenges, including the optimization of the number of start-up oil producers and injectors, and the selection of depletion mechanism which is preferably peripheral injection in this case. The type of well (vertical or horizontal), and completion intervals have to be investigated. In the case of horizontal wells, direction of the horizontal trajectory is always a difficult issue to decide as well as the optimized length of the horizontal section.Due to time constraints and the sheer size of the field areal extent (tens of kilometers) and the complex geology of the reservoir, it is not practical to construct a single full-field model which is expected to serve as an all-purpose simulation model that includes all of the reservoir attributes encompassing super-K layers, faults and fractures. This paper will discuss how to use an array of different reservoir simulation models to achieve the objectives within a timelimit dictated by the business plan requirements. Issues such as the number of start-up wells, the production plateau, type of wells, choice of completion intervals, optimized horizontal length, direction of horizontal trajectory can not be answered by one single model. However, each issue can be addressed by a specific model constructed for a single purpose. The development of an oil increment in Haradh is used to illustrate this concept.

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Understanding Waterflood Residual Oil Saturation of Four Carbonate Rock Types

Kamath

Meyer

Nakagawa

2001

SPE Annual Technical Conference and Exhibition

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Laboratory determination of residual oil saturation (ROS) in carbonate cores is sometimes uncertain due to wide pore size distribution, core scale heterogeneity, and complex wettability. The values obtained in laboratory tests may vary depending on flow rates, the type of samples (plugs or whole cores), and sample preparation techniques. The purpose of our study is to integrate modern flow visualization technology with conventional laboratory tools to provide a comprehensive picture of waterflood recovery behavior in four carbonate cores. Our data set comprise thin sections; mercury injection; 3–D porosity distribution; oilfloods and waterfloods on cleaned samples; and 3–D flow imaging of miscible floods, oilfloods, and waterfloods on restored state samples. The 3–D Computed Tomography (CT) images allowed us to understand the reasons for decrease in oil saturation observed with increased pressure drop in the corefloods; whether this is due to capillary-end effects, core scale heterogeneity, or actual reduction in ROS. We find that ROS values under field-rate flooding conditions (~ 1 psi/foot, Nc* ~ 10-8, lateral flood) are in the 30%-60% PV range. These ROS values reduce significantly as the pressure gradient applied during the floods is raised from field values to the much higher-pressure gradients sometimes used in laboratory testing (~ 100 psi/ft, Nc ~ 10-6). The carbonate samples with large pore-throat aspect ratios have the largest ROS values and the biggest variation with the pressure drop used in the waterfloods. Introduction ROS from Laboratory Floods. Most of the early laboratory waterfloods reported in the literature were conducted at high flow rates (Rapoport and Leas, 1953) to eliminate the capillary end effect at the outlet of the core sample. This method is still appropriate for very strongly water wet or very strongly oil-wet rocks. In the former case, waterflooding is a strong imbibition process, and we have a well-defined residual oil saturation (ROS) that is constant over a very wide range of flow rates. The ROS decreases only when flow rates become so large (Nc >10%5) that the trapped blobs of oil are mobilized. In the case of strongly oil-wet media, waterflooding is a drainage process. The waterflooded oil is in the form of continuos films, and residual oil saturation is theoretically close to zero. The issue here is one of determining the oil relative permeability at low oil saturation. Many reservoir rocks are now thought to be have intermediate or mixed wettability (Cuiec, 1991). Waterfloods in such systems are potentially a combination of drainage and imbibition. Laboratory measurements become a problem as we may experience a drainage capillary end effect, encouraging use of high rates; and there may also be a rate dependence in the imbibition trapping mechanism, suggesting the use of reservoir rates (Heaviside, 1991). Any decrease in the oil remaining in the core with increase in waterflood rate can be due to reduction in capillary end effects and/or due to change in the microscopic trapping mechanisms. The first factor is a laboratory artifact and does not reflect behavior in the field. The change in microscopic trapping is the true change in ROS and can be exploited by changing field conditions.

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Assessment of Residual Oil Saturation in a Large Carbonate Reservoir

Cited by 6 publications

References 0 publications

The Role of the Value of Information and Long Horizontal Wells in the Appraisal and Development Studies of a Brazilian Offshore Heavy-Oil Reservoir

The Role of the Value of Information and Long Horizontal Wells in the Appraisal and Development Studies of a Brazilian Offshore Heavy-Oil Reservoir

Logistic Approach in Using an Array of Reservoir Simulation and Probabilistic Models in Developing a Giant Oil Reservoir with Super-Permeability and Natural Fractures

Understanding Waterflood Residual Oil Saturation of Four Carbonate Rock Types

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