Experimental and numerical study of interaction of a pre-existing natural interface and an induced hydraulic fracture

Today's huge growth of energy need may not be fulfilled except using new source of unconventional energy that should be stimulated hydraulically. However, these reservoirs are non-homogeneous and contain various types of interfaces which make their fracturing treatment difficult. In this study, the interaction between the hydraulic fracture and a natural interface were investigated using analytical, numerical and experimental approaches. This was done by doing sensitivity analysis on some of the important parameters

A methodology for geomechanical modelling of in situ recovery (ISR) in fractured hard rocks

The extraction of geothermal energy, in situ minerals, liquid and gas hydrocarbons, and subsurface water are all constrained by the flow of fluid through fractured media in the earth’s crust, as is the viability of projects involving CO2 sequestration, nuclear and hazardous waste storage, hydrocarbon storage, and subsurface cavities. Subsurface fractures are the main fluid pathways as the matrix permeability is negligible in most rocks. In situ recovery (ISR) or in situ leaching (ISL), particularly in hard rock, poses some challenges currently. One of the main problems is the modelling of fluid flow in fractured rock masses, and this was the primary focus of this project. Modelling fluid flow in fractures can be done in many ways. The modelling showed that ISL in hard rock demonstrates potential. However, the modelling also exhibited the need for advancements in the fluid flow in fractures modelling area. In this paper comprehensive review of developed approaches for subsurface fracture mapping, processing and characterisation to build a fractured rock mass geometry and fluid flow simulation and mineral leachability along with examples were illustrated

Steps for conducting a valid hydraulic fracturing laboratory test

Several parameters are involved in a hydraulic-fracturing operation, which is a technique used mainly in tight formations to enhance productivity. Formation properties, state of stresses in the field, injecting fluid characteristics, and pumping rate are among several parameters that can influence the process. Numerical analysis is conventionally run to simulate the hydraulic-fracturing process. Before operating the expensive fracturing job in the field, however, it would be useful to understand the effect of various parameters by conducting physical experiments in the lab. Laboratory experiments are also valuable for validating the numerical simulations. Applying the scaling laws, which are to correspond to the field operation with the test performed in the lab, are necessary to draw valid conclusions from the experiments. Dimensionless parameters are introduced through the scaling laws that are used to scale-down different parameters including the hole size, pump rate and fluid viscosity to that of the lab scale. Sample preparation and following a consistent and correct test procedure in the lab, however, are two other important factors that play a substantial role in obtaining valid results. The focus of this peer-reviewed paper is to address the latter aspect; however, a review of different scaling laws proposed and used will be given. The results presented in this study are the lab tests conducted using a true triaxial stress cell (TTSC), which allows simulation of hydraulic-fracturing under true field stress conditions where three independent stresses are applied to a cubic rock sample

Numerical and Experimental Study of Hydraulic Fracture Active Source Monitoring

Hydraulic fracturing is one of the most common operations performed on oil and gas wells. As thehydraulic fracture propagation is so complex, monitoring techniques are used to determine the real-timegeometry of the induced fracture. In this work focus is made on numerical and experimental study ofactive monitoring of hydraulic fracture. Discrete element method is used for numerical simulation ofseismic wave transmission in a block of rock being hydraulically fractured. In this method the rock ismodeled by an assembly of round particles. On the other hand the results of an ultrasonic laboratoryexperiment in which a block of cement is fractured, are reported. Numerical and experimental deliversimilar results which are in agreement with those published in literature. The results show interesting information which can be applied for active monitoring of field hydraulic fractures

Nanofluids as Novel Alternative Smart Fluids for Reservoir Wettability Alteration

This chapter presents an account of two metal oxide nanoparticles (zirconium and nickel oxide) on basis of their structure, morphology, crystallinity phases, and their wetting effect on solid-liquid interface. As a preliminary step to sound understanding of process mechanisms; wettability, nanoparticles, and their relations thereof were scrutinized. To investigate the nanofluids wetting inclinations, complex mixtures of the nanoparticles and NaCl brine (ZrO2/NaCl; NiO/NaCl) were formulated and their technical feasibility as wetting agents tested via contact angle measurement. The result shows that the nanoparticles exhibit different structural and morphological features and capable of addressing reservoir wettability challenges owing to favorable adsorption behavior on the surface of the calcite which facilitated the wetting changes quantified by contact angle. We believe this study will significantly impact the understanding of wetting at solid-liquid interface which is crucial for recovery process optimization

A Realistic Look at Nanostructured Material as an Innovative Approach for Enhanced Oil Recovery Process Upgrading

With the continuous rise in energy demand and decline in reserves, the Petroleum Industries are constantly in search of inventive and novel approaches to optimize hydrocarbon recovery despite several decades of deployment of conventional and enhanced strategies. This chapter presents an in-depth analysis of nanomaterial (nanoparticles), their unique characteristics and potentials in relation to smart field development, enhanced oil recovery (EOR) and CO2 geosequestration. The particles surface functionalities, unique size dependent property, adsorption, and transport behavior were scrutinized. The materials precise role in enhancing reservoir parameters that influences rock–fluid interactions, and reservoir fluid distribution and displacement such as permeability, wettability, interfacial tension, and asphaltene aggregate growth inhibition were evaluated. The study argues that the application of nanoparticle based fluids as novel EOR approach offers more holistic measures, potentials, and opportunities than micro and macro particles and can stimulate the continuous evolution of EOR processes even under harsh reservoir conditions, thus, offering better benefits over conventional surface-active agents. We believe this study will significantly impact the understanding of EOR with respect to nanoparticles, which is crucial for augmenting reservoir processes and to accelerate the realization of nanoparticles for EOR and CO2 sequestration processes at industrial scale

Wettability alteration of oil-wet limestone using surfactant-nanoparticle formulation

Wettability remains a prime factor that controls fluid displacement at pore-scale with substantial impact on multi-phase flow in the subsurface. As the rock surface becomes hydrophobic, any oleic phase present is tightly stored in the rock matrix and produced (hydrocarbon recovery) or cleaned up (soil-decontamination) by standard waterflooding methods. Although surface active agents such as surfactants have been used for several decades for changing the wetting states of such rocks, an aspect that has been barely premeditated is the simultaneous blends of surfactants and nanoparticles. This study thus, systematically reports the behaviour of surfactants augmented nanoparticles on wettability alteration. Contact angle, spontaneous imbibition, and mechanistic approaches were adopted to assess the technical feasibility of the newly formulated wetting agents, tested over wide-ranging conditions to ascertain efficient wetting propensities. The contact angle measurement is in good agreement with the morphological and topographical studies and spontaneous imbibition. The wetting trends for the formulated systems indicate advancing and receding water contact angle decreased with increase in nanoparticle concentration and temperature, and the spontaneous water imbibition test also showed faster water-imbibing tendencies for nanoparticle-surfactant exposed cores. Thus, the new formulated nanoparticle-surfactant systems were considered suitable for enhancing oil recovery and soil-decontamination, particularly in fractured hydrophobic reservoirs

Contamination of silica surfaces: impact on water-CO2-quartz and glass contact angle measurements

CO2-wettability of sandstones is a key variable which determines structural and residual trapping capacities and strongly influences multi-phase fluid dynamics in the rock. An increasing number of researchers has now estimated this wettability by conducting contact angle measurements on quartz, however, there is a large uncertainty associated with the reported data. We demonstrate clearly that the main factor which leads to this broad data spread is due to surface contamination. It is clear that typically inappropriate cleaning methods were used which resulted in artificially high contact angle measurements. We used surface cleaning methods typically prescribed in the surface chemistry community and found that the water contact angle θ on a clean quartz substrate is low, 0–30°, and that θ increases with pressure. We conclude that quartz is strongly water-wet at high pressure conditions