INVESTIGATION OF NANO-POROSITY IN CARBONATE RESERVOIRS AND ITS ROLE IN UNDERSTANDING HYDROCARBON RESERVES AND RECOVERY ECONOMICS

ABSTRACT This study examines a Kuwaiti carbonate reservoir that is classified as a tight reservoir. In one core sample, the total porosity is reported to be 14%, of which 60% of its total porosity is estimated to be nano-pores. The objective of this study is to establish existence of these nano-pores and their whereabouts, and then investigates their nano-size role in hydrocarbon storage, economics and recovery mechanism. Characterizing nano-pores available in tight carbonate reservoirs starts with examining the constituents of the rock such as, mineral type and composition of grain, pore-size, and pore-size distribution. Nano-pore characterization has integrated several tools such as X-Ray Diffraction (XRD), Scattered Electron Microscopy (SEM), and mercury-Washburn Pore Size Distribution (PSD). The XRD will examine the rockfabric minerals associated with the nano-pores. The SEM analysis, which is a 2-dimensional scale technique, is associated with the study of the pore morphology as well as the study of the grain morphology; while the PSD is a 3-dimensional technique associated in measuring the total pore size distributions. As a result of integrating these tools, findings and subsequent inquiries are raised

A Novel Technique For The Quantitative Determination Of Wettability Of A Severely Heterogeneous Tight Carbonate Reservoir

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

Kuwaiti Carbonate Reservoir Oil Recovery Prediction Through Static Wettability Contact Angle Using Machine Learning Modeling

The objective of this study is to predict EOR efficiencies through static wettability contact angle measurement by Machine Learning (ML) modeling. Unlike conventional methods of measuring static wettability contact angle, the unconventional digital static wettability contact angle is captured and measured, then (ML) modeled in order to forecast the recovery based on wettability distribution phenomenon. Due to success in big data collection from reservoir imaging samples, this study applies data science lifecycle logic and utilizes Machine Learning (ML) models that can predict the recovery through wettability contact angles and thus identify the treatment of oil recovery for a candidate reservoir. Using developed morphological driven pixel-data and transformed numerical wettability contact angle data are acquired from Scanning Electron Microscope Backscattered Electron (SEM-BSE) for 27 fresh core samples from top to bottom of the reservoir. These samples are properly sequenced and then images are selected. Big data from imaging technology have been processed in a manner to train, and test the model accuracy. Applied Data Science Lifecycle technique, such as data mining, is utilized. Data Exploration Analysis (DEA) is implemented to understand and review data distribution as well as relationships among input features. Different supervised ML models to predict recovery are utilized and an optimal model is identified with an acceptable accuracy. The selected prediction model is applied to model the optimal recovery practice. Extreme Gradient Boosting (XGBoost) algorithm is utilized and found as a best-fit model for this Kuwaiti reservoir case practice. Moreover, decision tree and Artificial Neural Network (ANN) models could provide acceptable accuracy. Other supervised learning models were attempted and were not promising to provide feasible accuracy for this carbonate reservoir. The novel of this unique solution of the data-driven ML model is to predict recovery based on static wettability contact angles (?°). The static wettability contact angles (?°) and pore morphological features introduce an insights method to support reservoir engineers in making value-added decisions on production mechanisms and hydrocarbon recovery for their reservoirs. Hence, it improves the field development strategy

Practical Imaging Applications Of Wettability Contact Angles On Kuwaiti Tight Carbonate Reservoir With Different Rock Types

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

Are Natural Fractures In Sandstone Reservoir: Water Wet – Mixed Wet – Or Oil Wet?

This study accurately measures the wettability contact angle of native Kuwaiti sandstone reservoir that hosts mixed pore size distributions in both the tight sandstone matrix as well as the natural fracture (NF) embedded in it. Also, this study, effectively, investigates the geometrical size and shape of natural available voids whether matrix voids or NF voids captured in the rock 2D image frame system. Correspondingly, this study is, successfully, measure tight matrix, NF Pore wall, and NF pore opening wettability performance and recovery efficiency contributions inside the sandstone reservoir. A model pore/ grain contact angle wettability is generated. Therefore, this study thrives to enhance new physics that will advance reservoir characterization and production improvement through modeled and measured wettability contact angle. The prepared fresh tight sandstone rock sample in the form of rock fragment is imaged and characterized for porosity, permeability, and wettability contact angle in 2D format utilizing SEM-BSE imaging techniques. The generated images will be quantified using pre-defined logic for wettability contact angle measurement. The data generated will be used to estimate the wettability distribution. Each image captured will be investigated for a magnification of X51 (1 mm Scale). This magnification scale will ensure measurement of all possible pore/ grain petrophysical porosity & permeability features, as well as wettability contact angle of 3 region representations for the tight matrix, the natural fracture pore wall, and the inside fracture void. From measured data and computed logics, the majority portions of natural pore voids and pore-walls are medium-water-wet; however, some fracture-pore-walls show mixed and strongly oil wetting preference. The main factors in the understanding the fracture wettability are pore size distribution and pore morphology that suggests the wettability affinity likelihood. This study shows 3 natural pore regions: tight matrix, natural fracture pore wall, and inside the natural void space. These regions are necessary to characterize wettability behavior for oil production and crude oil reservoir recovery schemes, especially in EOR schemes such as water production and/ or water injection operations. Also, the fracture-to-matrix ratio shows some new interesting features characterizations

Experimental Investigation of Environmentally Friendly Drilling Fluid Additives (Mandarin Peels Powder) to Substitute the Conventional Chemicals Used in Water-Based Drilling Fluid

The non-biodegradable additives used in controlling drilling fluid properties cause harm to the environment and personal safety. Thus, there is a need for alternative drilling fluid additives to reduce the amount of non-biodegradable waste disposed to the environment. This work investigates the potential of using mandarin peels powder (MPP), a food waste product, as a new environmentally friendly drilling fluid additive. A complete set of tests were conducted to recognize the impact of MPP on the drilling fluid properties. The results of MPP were compared to low viscosity polyanionic cellulose (PAC-LV), commonly used chemical additive for the drilling fluid. The results showed that MPP reduced the alkalinity by 20-32% and modified the rheological properties (plastic viscosity, yield point, and gel strength) of the drilling fluid. The fluid loss decreased by 44-68% at concentrations of MPP as less as 1-4%, and filter cake was enhanced as well when comparing to the reference mud. In addition, MPP had a negligible to minor impact on mud weight, and this effect was resulted due to foaming issues. Other properties such as salinity, calcium content, and resistivity were negligibly affected by MPP. This makes MPP an effective material to be used as pH reducer, a viscosity modifier, and an excellent fluid loss agent. This work also provides a practical guide for minimizing the cost of the drilling fluid through economic, environmental, and safety considerations, by comparing MPP with PAC-LV

Experimental Investigation of Bio-Enhancer Drilling Fluid Additive: Can Palm Tree Leaves Be Utilized as a Supportive Eco-Friendly Additive in Water-Based Drilling Fluid System?

Serious problems will be presented due to using conventional chemical additives to regulate the drilling mud properties, as they have health, safety, and environmental side effects. Thus, there is a considerable necessity for alternative multifunctional bio-enhancer drilling mud additives, which can assist in optimizing the drilling fluid specifications and enhance its effectiveness with the least effects on the environment and the drilling personnel safety. The effects of adding two concentrations of palm tree leaves powder (PTLP) to water-based mud were conducted under fresh and aged conditions using standard API drilling fluids testing methods such as rheometer/viscometer, pH meter and temperature, and filter press. All tests results were minutely recorded to understand the influence of PTLP additives on the drilling mud properties. The results indicated that PTLP as an effective material to be used as pH reducer, viscosity reducer, and as an excellent filtration loss control agent under the surface and sub-surface conditions. Thus, PTLP has excellent feasibility to be utilized as biodegradable drilling mud additive replacing or at least supporting other conventional chemical additives, which have usually been used for the same purposes such as lignosulphonate, chrome-lignite, and Resinex. Finally, this work can serve as a practical guide for minimizing the cost of the drilling fluid and reducing the amount of non-biodegradable waste disposed to the environment

Characterization and permeability modeling of complex Mauddud-Burgan carbonate reservoir

Mauddud-Burgan is a carbonate reservoir located in southeast Kuwait which is known for its structural complexity, especially in the context of horizontal drilling activities...This study addresses a detailed characterization of Mauddud-Burgan formation to expedite future reservoir planning and development. The detailed analysis involved seven aspects of reservoir characterizations, including: geological study, thin-section study, XRD study, SEM study, core study, well logging study and well test analysis....The principal objective of the study is to integrate results obtained from experimental measurements of rock samples from Well A, and, to build a model based on this integration. A new, unconventional approach of modeling based on Neural Networks is used to characterize the permeability of Mauddud-Burgan --Abstract, page iii

Will Coupling Low Salinity Water and Steam Flooding for Heavy Oil Affect the Rock Properties of Sandstone Reservoirs? An Experimental and Simulation Study

Recently Al-Saedi and Flori et al. (2018d) studied the potential of low salinity alternating steam flooding (LSASF) in laboratory sandstone cores, and the results were promising for increasing heavy oil recovery. In this study, we investigate the effect of LSASF on rock properties for the Bartlesville Sandstone Reservoir. These core samples contain high viscous oil (600 cp) with an average permeability of 80 mD. Combining low salinity (LS) water flooding and steam flooding is a novel idea that takes advantage of the relative strengths of both methods. To investigate the proposed new method and the role of LSASF, core flooding experiments, contact angle measurements, spontaneous imbibition tests, zeta potential tests, and reactive transport model were performed. The laboratory experiments showed that optimum recovery is achieved by diluting the FW 40 times and using the same water in a shorter steam cycle. Permeability measurements before and after core flooding revealed that the higher the salinity, the more permeability decreased. Steam can enhance the performance of LS water by reducing precipitation, increasing permeability, and dissolving minerals, and in turn, increasing oil recovery. Flooding the core with both LS water and steam resulted in more water wetness in the sandstone cores. Comparing the cores that were flooded with only LS water with the cores flooded with both LS water and steam, lower water wetness was obtained for the cores that were flooded only with LS water. The results were deliberated concerning wettability change processes by LS Water and steam. The zeta potential tests confirmed that as the salinity decreases, the zeta potential decreases too. Also, measuring contact angle before and after core flooding resulted in more water wetness. Spontaneous imbibition tests were in line with all other tests. The reactive transport modeling confirmed the crucial role of diluting FW in decreasing the number of the most effective kaolinite edges Si—O-- and Al--O--, which explains why lowering the salinity gives additional oil recovery

Experimental Study of Low Salinity Water Flooding: The Effect of Polar Organic Components in Low-Permeable Sandstone Reservoir

Low salinity (LS) water flooding in the sandstone reservoir is of pronounced interest of the prospective for improved oil recovery. In this study, laboratory experiments in low-permeable sandstone core plugs saturated with various crude oil containing different acid numbers were presented. Several low-permeable sandstone cores (1-3 mD) were taken from Bartlesville Sandstone Reservoir from Eastern Kansas were successively flooded with seawater and different LS water. The reservoir cores were cleaned and saturated with formation water (FW) and then aged in three kinds of crude oil (different acid numbers) for six weeks at 90°C. To evaluate LS water in the low-permeable reservoir core plugs, core flooding tests were performed. Contact angle and spontaneous imbibition tests were also carried out. The results obtained from LS water flooding showed that an improvement in oil recovery up to 12% of the original oil in place when the acid number (AN) and core permeability were low. The water wetness, and in turn, the oil recovery reduced with increased crude oil\u27s AN and as the permeability increased. The contact angle and spontaneous imbibition tests confirmed the appropriate wettability change is attainable with LS water flooding. The results were deliberated in relation to wettability change processes by LS Water