We interpreted a series of single-well-chemical-tracer-tests (SWCTTs) estimating residual oil (SORW) to base high salinity waterflood, low salinity waterflood and subsequent polymer flood conducted on a Greater Burgan well. Interpretation of the tests requires history matching of the back-production of partitioning and non-partitioning tracers which is impacted by differing amounts of irreversible flow and differing amounts of dispersion as well as the amount of residual oil.
We applied the state-of-the-art chemical reservoir simulator (UTCHEM) and an assisted history matching tool (BP’s Top-Down-Reservoir-Modeling) to interpret the tests and accurately quantify uncertainty in residual oil saturations post high salinity, low salinity, and polymer floods. Two optimization algorithms (i.e., Genetic algorithm (GA) and Particle-Swarm-Optimization (PSO)-Mesh-Adaptive-Direct-Search (MADS) algorithms) were applied to better address the uncertainty.
Our results show a six saturation unit decrease in SORW post low salinity with no change to the SORW post polymer. This is in-line with our expectations - we expect no change in SORW post-polymer as the conventional HPAM, which does not exhibit visco-elastic behavior, was used in the test. We demonstrate that history matching the back-produced tracer profiles is a robust approach to estimate the SORW by showing that three-or four-layer simulation model assumption does not change the SORW estimated. We accounted for the uncertainty in partition-coefficient in our uncertainty estimates.
We present several innovations that improve history matching back-produced tracer profiles; hence, better SORW estimations (e.g., different level of dispersivity for individual simulation layers to account for different heterogeneity level as opposed to assuming a single dispersion for all layers). We generate more robust estimates of uncertainty by finding a range of alternative history matches all of which are consistent with the measured data.
Alhuraishawy, Ali K. (Iraqi Ministry of Oil / Reservoir and Fields Development Directorate) | Jaber, Ahmed Khalil (Iraqi Ministry of Oil / Reservoir and Fields Development Directorate) | Aljawad, Sameer Noori (Iraqi Ministry of Oil / Reservoir and Fields Development Directorate) | Bai, Baojun (Missouri University of Science and Technology) | Wei, Mingzhen (Missouri University of Science and Technology) | Baker, Hussein Ali (Baghdad University) | AL-Bazzaz, Waleed Hussien (Kuwait Institute for Scientific Research)
The limitations of oil recovery from carbonate reservoirs are fractures and oil-wet conditions. To overcome the reservoir heterogeneities and reduce fracture transmissibility, preformed particle gel was applied in injector wells. Experimentally, low salinity waterflooding was applied to change the core wettability from oil-wet to water wet for enhanced oil recovery. However, both processes have limitations that cannot be resolved using a single method. A nonuniform fracture width and uniform fracture width models were built using carbonate cores to evaluate the coupling low salinity waterflooding and preformed particle gel in fractured cores and how could be used to improve in-depth water diversion treatment. The results showed that low salinity waterflooding improved in-depth water diversion when injected after PPG directly while seawater showed less effect than low salinity waterflooding. Also, the uniformity of fracture had a significant effect on plugging efficiency oil recovery factor from fractured reservoirs.
Rognmo, Arthur U. (University of Bergen) | Al-Khayyat, Noor (University of Bergen) | Heldal, Sandra (University of Bergen) | Vikingstad, Ida (University of Bergen) | Eide, Øyvind (University of Bergen) | Fredriksen, Sunniva B. (University of Bergen) | Alcorn, Zachary P. (University of Bergen) | Graue, Arne (University of Bergen) | Bryant, Steven L. (University of Calgary) | Kovscek, Anthony R. (Stanford University) | Fernø, Martin A. (University of Bergen)
The use of nanoparticles for CO2-foam mobility is an upcoming technology for carbon capture, utilization, and storage (CCUS) in mature fields. Silane-modified hydrophilic silica nanoparticles enhance the thermodynamic stability of CO2 foam at elevated temperatures and salinities and in the presence of oil. The aqueous nanofluid mixes with CO2 in the porous media to generate CO2 foam for enhanced oil recovery (EOR) by improving sweep efficiency, resulting in reduced carbon footprint from oil production by the geological storage of anthropogenic CO2. Our objective was to investigate the stability of commercially available silica nanoparticles for a range of temperatures and brine salinities to determine if nanoparticles can be used in CO2-foam injections for EOR and underground CO2 storage in high-temperature reservoirs with high brine salinities. The experimental results demonstrated that surface-modified nanoparticles are stable and able to generate CO2 foam at elevated temperatures (60 to 120°C) and extreme brine salinities (20 wt% NaCl). We find that (1) nanofluids remain stable at extreme salinities (up to 25 wt% total dissolved solids) with the presence of both monovalent (NaCl) and divalent (CaCl2) ions; (2) both pressure gradient and incremental oil recovery during tertiary CO2-foam injections were 2 to 4 times higher with nanoparticles compared with no-foaming agent; and (3) CO2 stored during CCUS with nanoparticle-stabilized CO2 foam increased by more than 300% compared with coinjections without nanoparticles.
We provide experimental evidence of wettability alteration using seawater salinity brine of an oil-wet system composed of a three-dimensional carbonate micromodel, crude oil, and connate-water brine salinity. We designed this procedure as a first step for evaluation of using seawater as an Improved Oil Recovery (IOR) agent. Our innovative design combines two main experimental best practices: micromodels, for repeatable experiments and X-ray computed tomography (CT) as a non-invasive technique for monitoring in situ fluid distribution. Both practices merge into a new three-dimensional micromodel set-up that uses only reservoir species (no high x-ray contrast chemicals).
Wettability alteration plays a key role to improve oil recovery from matrix blocks surrounded by water-invaded fractures in carbonate reservoir rocks. We designed a simple and replicable experimental apparatus and procedure to quantify contact angle distributions inside of porous media with a controlled level of heterogeneity in roughness and mineralogy. This experiment consists of visualizing the in-situ contact angle distribution of the aqueous phase inside a three-dimensional carbonate micromodel. Using Micro Computerized Tomography (MicroCT), we obtained three-dimensional images of fluid distribution with a voxel size of 3.8 microns.
We successfully studied the wettability state after connate water displacement and we also altered wettability of the carbonate porous medium from more oil wet to less water wet conditions. The water contact angle of the ganglia showed a 70% reduction in contact angle from an oil-wet to a water-wet system using an approximate seawater salinity and a 63% reduction in contact angle in the case of a full synthetic seawater. The initial average contact angles were 140° and 142° for the two solutions, respectively. After EOR seawater flooding, the average contact angle declined to 44° and 51°, respectively.
Abdelfatah, Elsayed (Chemical and Petroleum Engineering Department, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada) | Wahid-Pedro, Farihah (Chemical and Petroleum Engineering Department, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada) | Melnic, Alexander (Chemical and Petroleum Engineering Department, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada) | Vandenberg, Celine (Chemical and Petroleum Engineering Department, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada) | Luscombe, Aidan (Chemical and Petroleum Engineering Department, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada) | Berton, Paula (Chemical and Petroleum Engineering Department, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada) | Bryant, Steven (Chemical and Petroleum Engineering Department, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada)
Waterflooding of heavy oil reservoirs is commonly used to enhance their productivity. However, preferential pathways are quickly developed in the reservoir due to the significant difference in viscosity between water and heavy oil, and hence, the oil is trapped. Here, we propose a platform for designing ultra-low IFT solutions for reducing the capillary pressure and mobilizing the heavy oil.
In this study, mixtures of organic acids and bases were formulated. Three different formulations were tested: (i) Ionic liquid (IL) formulation where bulk acid (4-dodecylbenzene sulfonic acid) and base (Tetra-
The IL and ABs formulation are acidic solutions with pH around 3. The ASBs formulation is highly basic with a pH around 12. Non of the formulations salted out below 14 wt% of NaCl. While conventional surfactant, SDBS, precipitated at salt concnetration less than 2 wt% of NaCl. The formulation solutions (1 wt%) have different optimum salinities: 2.5 wt% NaCl for ASBs, 3 wt% NaCl for IL and AB. Although IL and AB have the same composition and molar ratio of the components, their performances are completely different, indicating different intermolecular interactions in both formulations. Corefloods were conducted using sandpack saturated with Luseland heavy oil (~15000 cP) and at fixed Darcy velocity of 12 ft/day. A slug of 1 PV of each formulation was injected after waterflooding for 5 PV and followed by 5 PV post-waterflooding. In the hydrophilic sandpacks, IL and AB formulation produced an oil bank, consisting mainly of W/O emulsion, with oil recovery that is 1.7 times what was recovered by 11 PV of waterflooding solely. Majority of the oil was recovered in the 2 PV of waterflood following the IL slug. ASBs formulations produced O/W emulsions with prolonged recovery over 5 PV waterflooding after the ASB slug. The recovery factor for ASBs was 1.6 times that recovered for 11 PV of waterflooding only. In the hydrophobic sandpacks, The ASB formulation slightly increased the recovery factor compared to only waterflooding. While for IL and AB formulation, the recovery factor decreased.
This work presented a novel platform for tuning the recovery factor and the timescale of recovery of heavy oil with a variable emulsion type from O/W to W/O depending on the intermolecular interactions in the system. The results demonstrate that the designed low IFT solutions can effectively reduce the capillary force and are attractive for field application.
A new cased-hole porosity measurement has been developed for a four-detector pulsed-neutron logging tool. The measurement is based on a capture count rate ratio from two different detectors. To determine an accurate porosity, the ratio is characterized in the laboratory in order to establish a ratio-to-porosity transform. To account for varying measurement conditions in the field, environmental corrections, based on laboratory studies and computer simulation, are applied. As an alternative to environmental corrections, the capture ratio can also be actively compensated for the environment by using the results of a dual-exponential fit to the capture time decay spectrum. In particular, we can compensate for the borehole fluid salinity by using the borehole component of the dual-exponential fit, and we can compensate for the effective density of the borehole environment by using an inelastic ratio derived from the capture subtracted burst yields. The final porosity measurement has been shown to provide accurate results in the field through a comparison with data from open-hole logs.
In this paper the dielectric constant of shaly sands both the real and imaginary parts is investigated and compared. An empirical model has been developed in the one MHz to one GHz frequency range for the real part of the dielectric constant. The equations developed involve the same pore systems as those governing the conductivity response. The dielectric constant contains an additionalfrequency independent high frequency limit. The dispersive terms are due to the clays and interfacial phenomena. The salinity and frequency dependence of these parameters are then discussed.
This salinity dependence of the dielectric model is compared to the salinity dependence both predicted and measured for the conductivity. Conductive inclusions are modeled similar to previously published work (
After nearly thirty years of research and development, it is now commonly agreed that Low Salinity Waterflood (LSW) is an attractive enhanced oil recovery (EOR) method because of its incremental oil recovery performance, reasonable operating cost and low environmental impact compared to conventional waterflood and other EOR processes. From the past studies, LSW is known as a process that comprises many mechanisms, i.e. multiple ion exchanges, wettability alteration, complex geochemical reactions, and fines migration and deposition. However, most studies in the literature have only focused on a single recovery mechanism, with varying, sometimes contradictory conclusions. This paper presents: (1) a comprehensive model that takes into account all the different important physics in LSW, i.e. fines transport, geochemistry and wettability alteration; (2) validation with a core-flood experiment; and (3) field-scale optimization of LSW.
A model for fines transport has been developed and incorporated in an Equation-of-State compositional reservoir simulator with geochemistry and wettability alteration modeling. The proposed model is capable of accounting for complex transport phenomena of fines (clay) particles in porous media including fines deposition, entrainment, and plugging. The simulator also considers physical phenomena in the oil/rock/brine system such as aqueous chemical equilibrium, rate dependent mineral reactions, multiple ion exchanges, and relative permeability alteration due to wettability changes. Validations with a LSW core-flood experiment were carried out, which provide insights into the important mechanisms for the incremental oil recovery by LSW.
The proposed model shows good agreement in terms of oil recovery and pressure drop with a benchmark LSW core-flood experiment which was conducted with a non-polar oil and in which migration of clay particles and their plugging of pores were considered as the main recovery mechanism. It is shown that the proposed model can efficiently capture the important physics in LSW processes related to fines transport. The impact of formation damage during LSW can be efficiently evaluated using this model. Finally, an optimization workflow helps maximize the recovery factor of the LSW process.
To our knowledge, this paper describes one of the first LSW mechanistic models to capture the three principal mechanisms of LSW, i.e. fines transport, geochemistry, and wettability alteration. Excellent match with laboratory experiments and field-scale optimization reinforce validity of the model. The proposed workflow can be extended to other recovery methods such as Low-Salinity Polymer or Low-Salinity Alkali-Surfactant-Polymer.
Almeida da Costa, Alana (Universidade Federal da Bahia) | Jaeger, Philip (Eurotechnica GmbH) | Santos, Joao (Láctea Científica) | Soares, João (University of Alberta) | Trivedi, Japan (University of Alberta) | Embiruçu, Marcelo (Universidade Federal da Bahia) | Meyberg, Gloria (Universidade Federal da Bahia)
Low salinity waterflooding and CO2 injection are enhanced oil recovery (EOR) methods that are currently growing at a substantial rate worldwide. Linking these two EOR methods appears to be a promising approach in mature fields and for the exploration of post- and pre-salt basins in Brazil. Moreover, the latter reservoirs already have high CO2 content in the gas phase. Interfacial phenomena between fluids and rock in low salinity brine/CO2 environment still remain unclear, particularly the wettability behavior induced by the pH of the medium. In this study, coreflooding experiments, zeta potential, contact angle, interfacial tension (IFT), and pH measurements at ambient and reservoir conditions were performed to investigate the influence of the rock composition and brine/CO2 mixtures at different pH values for low salinity water-CO2 EOR (LSW-CO2 EOR) applications in Brazilian reservoirs. Brazilian light crude oil, pure CO2, and different brine solutions were used to represent the fluids in actual oil reservoirs. The experiments were carried out on Botucatu sandstone samples, with mineralogy determined by energy dispersive X-ray analysis. Coreflooding experiments were conducted by injection of 10 pore volumes of high salinity water followed by low salinity water. Contact angles, IFT and pH measurements at atmospheric and elevated pressures were performed in a high-pressure view cell (
Kar, Taniya (Reservoir Engineering Research Institute, Palo Alto, CA) | Chávez-Miyauchi, Tomás-Eduardo (Universidad La Salle México) | Firoozabadi, Abbas (Reservoir Engineering Research Institute, Palo Alto, CA) | Pal, Mayur (North Oil Company, Doha, Qatar)
Low salinity water injection when effective in increasing oil recovery is often thought to be through increase in water wetting. Recently, oil-water interfacial rheology has been suggested to be related to oil recovery from low salinity water flooding. We have also discovered that addition of a very small amount of a functional molecule in the injection brine increases oil recovery significantly. Quantitative effect of interfacial elasticity and the effect of rock on oil recovery is investigated at 100 ppm concentration in this work for the first time. A light crude oil is used in four sets of waterflooding experiments in a carbonate rock. The injection brine is modified by adding 100 ppm of a non-ionic surfactant. To understand the recovery performances, interfacial viscoelasticity, interfacial tension and contact angle measurements are performed using brines of varying salinities. In interfacial rheology the effect of equilibration of the aqueous phase with the rock is also investigated. Additionally, adsorption of the surfactant in the carbonate rock is investigated for various aqueous phases via UVvis spectrometry. Crude oil, calcite and reservoir brine show moderate oil-wetting behavior. Addition of surfactant molecules makes the system more water-wet, however, the change is not pronounced. From coreflooding experiments, addition of surfactant in high salinity brine increases recovery by over 20% which we interpret to be due increase in interface elasticity. The phase angle which is a direct measure of interface elasticity decreases by 70% in an aqueous phase at about 4 wt% salt due to the surfactant. High interface elasticity reduces oil snap off and increases oil recovery. An effective molecule dissolved in water can increase the interface elasticity significantly. In relation to low salinity water injection we have established that there is an optimum salt concentration for high oil recovery. The injection of an aqueous phase without salt gives a lower recovery than injection of say 0.1 wt% salt in the injected water.
We have introduced a new IOR process based on interface elasticity which requires a very low concentration of a non-ionic surfactant. The process is neither through wettability alteration nor through significant change in IFT. The chemical we have used is environmentally friendly and of low cost. It has very low adsorption onto the rock surface.