TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThis paper presents an in depth study for a field-wide application of Maximum Reservoir Contact (MRC) wells along with smart well completions complemented by openhole expandable tubular to develop Haradh Increment-3, the southernmost area of the greater Ghawar Field. The reservoir represents a heterogeneous matrix permeability background, with geological discontinuities such as faults, fractures, and stratiform high permeability streaks. An MRC is a multi-lateral horizontal well with more than 5 km. of total contact with the reservoir rock (1,2) .This paper illustrates how an MRC well with smart completion was designed with objectives for higher productivity, better pressure transfer between laterals, delay in water encroachment by down hole control, and higher cumulative production. The design was based on highly detailed dual porosity and dual permeability cross-sectional, sector and full field simulation models in addition to field trials.
The common wisdom is that gravity methods have limited application in the oil industry although they have long been available. The main use of gravity has been for exploration purposes. 4D microgravity monitoring is another new promising gravity application to monitor changes of fluid contacts. Some successful 4D monitoring surveys have been conducted in the industry revealing that this technique is a proven technology in monitoring of gas-water contacts.This paper studies the ability of microgravity to capture movement of the injected water in a giant carbonate field. The oilwater case is more difficult due to the significantly lower density contrast as compared to the gas-water case. Monitoring water floodfront in the field is a key factor in applying successful reservoir management practices to maximize recovery and prolong the field life. The monitoring of inter-well fluids would characterize any pre-mature water breakthrough to allow planning and design of appropriate remedial well interventions. The current applied monitoring tools such as carbon-oxygen and resistivity logs can only detect fluids near to the wellbore due to their shallow radius of investigation. For the study field, 4D seismic cannot be used for fluid movement detection due to issues related to formation acoustics impedance and data quality.The study has shown that surface microgravity monitoring could successfully detect the inter-well fluid changes due to water injection with a high precision tool (0.01 microgal). It also shows that microgravity monitoring can capture water bodies located hundreds of meters away from the location of the 4D measurement.
This paper discusses a field example of capillary pressure effects on down hole formation tester pressure measurements and oil-water contact estimation. Capillary pressure effects are investigated as functions of mud invasion, mobile formationwater, and rock wettability. Specifically, the effects of mudfiltrate invasion on formation tester probe pressures are quantified in terms of the error margin on the oil-water contact estimate. In the field example, a fluidpressure gradientof about .45psi/ft was established from the bottom to the top of the reservoir, which is indicative of a water bearing formation. On the other hand, bottom hole fluid samples with the Modular Formation Dynamics Tester (MDTTM) showed a 100%oil recovery in shallow intervals, moderate oil-cut recovery in the intermediate intervals, and lowoil-cut recovery in the deep intervals. The purpose of this paper is to use formation tester information from the field example well, offset delineation wells, and reservoir behavior information, to support and explain that the apparent gradient in this case is not a true representative of the fluid gradient in the reservoir, rather, it represents the water phase gradient created by filtrate invasion and mobile water. A simulation model was developed, based on reservoir properties and laboratory measured capillary pressures, to simulate the formation saturation as a function of mud filtrate invasion and mobile water. Log-derived water saturations were used as a guidance, and ultimately, the model was used to predict the apparent pressure readings by the formation tester. Together with the understanding of reservoir behavior derived from the simulation model, field data from all delineation wells were used to define the effects of mud filtrate invasion on formation tester pressure measurements. Consequently, the error margin on the oil-water contact estimate is benchmarked. Based on the field evidence, the paper also discusses which methodology is most accurate to use in the oil-water contact delineation in the field area of interest. Introduction In our field case example, oil-cut samples were retrieved from the formation with apparent water gradient in well A2, located in Haradh Increment-3 area, Arab-D reservoir. In order to shed some light on the observed phenomenon we shall present the results of the MDT job, identify the pressure points and zonations that samples were collected from, prior to the discussion and explanation of the observations. Firstly in the discussion, the definition of the oil-water contact, free water level, capillary pressure, and all relevant technical attributes will be presented. Secondly, the wettability of Haradh Arab-D rocks must be established. Then a field case will be used to illustrate the capillary effects of filtrate and mobile water upon the measured pressures using data from well A2 as well as data from relevant wells, e. g. A1, A3 and A4. Lastly, all reservoir parameters are put together in amodel to simulate the impact of capillarity on measured pressures.
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