This study focuses on a tight carbonate reservoir which is located in Northern Kuwait and is classified as an unconventional reservoir. A practical imaging technique of wettability contact angle (θ°) presents "big data" as well as relative-permeability (Krw and Kro) measurements. Also, modeling, through rock image technology, the vast well-documented grain/pore boundary morphology available inside fresh rock fragments have achieved good results. Conventional laboratory relative-permeability experiments are expensive and time-consuming. This study introduces a novel method to measure/calculate relative permeability through fast, less expensive, non-destructive, and environmentally friendly techniques of imaging technology. One tight carbonate reservoir is selected, imaged, processed, analyzed, and then modeled using several pore diameter morphological models. The images are captured using a backscattered electron microscopy BSE-SEM technology analyses. In this study, two-dimensional images are used to characterize the morphology of selected samples grains and pores, using a two-step technique. In the first step, the image is captured using a backscattered electron detector (BSE), digital electron microscopy imaging, and pore-counting processing technology. All of the sample grain/pore features captured in the image are reported in micrometer units. In the second step, the pore area of such features is scanned using image analysis software that can accurately measure several morphological parameters of pore and grain spaces. A robust technique of visual estimate is used, which has the advantage of speeding the image analysis process. The visual analysis software tool counts different pores and counts grains and also measures their shapes and sizes which are crucial for relative permeability calculations. Several pore morphological models have been considered for optimum accuracy comparisons, including pore/grain relationships (area/perimeter), pore contact angle (θ), and pore count. Relative permeability is calculated based on the area of the pore/grain features measured from two-dimensional images. The study objectives are to accurately measure the wettability contact angle of huge pore geometries using 2D image technology to understand the nature of the pore network in the candidate reservoir. To study the relative permeability of internal influences of pore and grain morphology needed for enhanced oil recovery/improved oil recovery (EOR/ IOR) future programs. And, finally, to measure relative permeability faster and more accurately.
The objective of this study is to accurately measure the wettability contact angle of a cretaceous carbonate reservoir in a vertical well set-up known for as an unconventional tight carbonate oil reservoir. Also, to investigate the relative heterogeneity of these samples using digitally captured images; these images accurately capture natural pore-system in this carbonate rock samples and their wettability performance attributed towards building a vertical depth wettability/ heterogeneity model. To capture, measure and model natural tight matrix static contact angle wettability in order to understand their new physics that will advance unconventional tight oil reservoir characterization. Entire vertical well depth reservoir core rock samples, in the form of rock fragments, are selected, then imaged, and then characterized for porosity, permeability, tortuosity/ heterogeneity, and pore/ grain-wettability contact angle in 2D format utilizing SEM-BSE imaging techniques. The generated big data images will be quantified using pre-defined logic for tortuosity/ heterogeneity and wettability contact angle measurement. Each rock sample will process several images captured at X40 (mm), X400 (μm), and X4000 (nm) magnifications and will investigate wettability/ heterogeneity relationships for unconventional tight pore system from the entire vertical depth. From measured data and computed logics, the major portions of captured rock investigated show water wet tendency. The wettability distribution in the vertical 250 feet shows strong to medium and even weak water-wet system variation (θ = 10° - θ = 90°). The dominant wettability is medium-water-wet (θ = 30° - θ = 60°), and it is found in the middle section of the vertical column. Medium-water-wet indicates a good candidate for secondary recovery water injection development programs. This study includes tortuosity/ heterogeneity quantifications from imaging 2D technology which is valuable in understanding vertical/ horizontal fluid movements. The authors feel that this study will narrow the gap in understanding contact angle wettability, heterogeneity characterizations from static conditions viewpoint and hence, the reservoir crude oil recovery vertical profile history from vertical rock samples.
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