Mohd Zaidi Jaafar

Laboratory Measurements and Numerical Modeling of Streaming Potential for Downhole Monitoring in Intelligent Wells

Downhole monitoring of streaming potential, using electrodes mounted on the outside of insulated casing, is a promising new technology for monitoring water encroachment toward an intelligent well. However, there are still significant uncertainties associated with the interpretation of the measurements, particularly concerning the streaming potential coupling coefficient. This is a key petrophysical property that dictates the magnitude of the streaming potential for a given fluid potential. We present the first measured values of streaming potential coupling coefficient in sandstones saturated with natural and artificial brines relevant to oilfield conditions at higher-than-seawater salinity. We find that the coupling coefficient in quartz-rich sandstones is independent of sample type and brine composition as long as surface electrical conductivity is small. The coupling coefficient is small in magnitude, but still measurable, even when the brine salinity approaches the saturated concentration limit. Consistent results are obtained from two independent experimental setups, using specially designed electrodes and paired pumping experiments to eliminate spurious electrical potentials. We apply the new experimental data in a numerical model to predict the streaming potential signal that would be measured at a well during production. The results suggest that measured signals should be resolvable above background noise in most hydrocarbon reservoirs. Furthermore, water encroaching on a well could be monitored while it is several tens to hundreds of meters away. This contrasts with most other downhole monitoring techniques, which sample only the region immediately adjacent to the wellbore. Our results raise the novel prospect of an oil field in which the wells can detect the approach of water and can respond appropriately.

Fault Interpretation Using Image Logs

In oil and gas reservoirs, having the faults attributes such as dip inclination degree, dip azimuth, strike, location of the faults and the type of the faults is essential due to their effect on production rate. Therefore, in this work a new method will be introduced to provide this geological information. By using the Formation Micro Imager (FMI) tool, the fault interpretation job will be done in one of the Iranian production wells, located in Gachsaran field.

Monitoring Foam Stability in Foam Assisted Water Alternate Gas (FAWAG) Processes Using Electrokinetic Signals

The natural pressure in hydrocarbon reservoirs is only sufficient in producing small amount of hydrocarbon at the end of the depletion stage. Therefore, in order to enhance or increase the hydrocarbon recovery, water or other fluids are injected into the formation to extract the hydrocarbon from the pore space. This common practice is known as Improved or Enhanced Oil Recovery (IOR or EOR). Foam is purposely used in some of the EOR displacement processes in order to control the mobility ratio, hence improving the volumetric sweep efficiency. The efficiency of a foam displacement process in EOR depends largely on the stability of the foam films. In laboratory, foam stability is usually measured through physical observation of the foam bubble in a glass tube. Unfortunately, this direct observation is not possible in the reservoir. Therefore, indirect measurement such as the measurement of electrokinetic signal would be a better alternative. This study aims to determine the correlation between the foam stability and the associated streaming potential signals which resulted from the flowing fluid in foam assisted water alternate gas (FAWAG) process. The experimental work will be conducted at the Reservoir and Drilling Engineering Laboratories at the Faculty of Petroleum and Renewable Energy Engineering (FPREE), UTM. The investigation includes sample preparation, sample analysis, displacing fluid formation, rheological properties test and electrokinetic signal measurement by using NI Data Acquisition System (NIDAS). It is expected that the burst of the foam bubble will change the pattern of the electrokinetic signals. The research findings could lead to a new approach in monitoring a FAWAG process. Application in the real field could benefit the oil and gas industry in term of making the EOR process more efficient and more economic.

Transient pressure analysis for vertical oil exploration wells: a case of Moga field

Reservoir engineers use the transient pressure analyses to get certain parameters and variable factors on the reservoir’s physical properties, such as permeability thickness, which need highly sophisticated equipments, methods and procedures. The problem facing the exploration and production teams, with the discoveries of new fields, is the insufficiency of accurate and appropriate data to work with due to different sources of errors. The well-test analyst does the work without reliable set of data from the field, thus, resulting in many errors, which may consequently cause damage and unnecessary financial losses, as well as opportunity losses to the project. This paper analyzes and interprets the noisy production rate and pressure data with problematic mechanical damage using a deconvolution method. Deconvolution showed improvement in simulation results in detecting the boundaries. Also, high-risk area analysis with different methods being applied to get the best set of results needed for subsequent operations.

Adsorption of aerosol-OT on sand and shale at high sodium salt concentration

Surfactant flooding is a method for additional recovery of oil from partially depleted reservoirs by changing the interfacial tension. During the application of surfactant into a reservoir, a certain loss in the high equivalent weight fraction occurs. These surfactant molecules are the most efficient in lowering the interfacial tension between reservoir brine and crude oil. Introducing the surfactant to rock sediment may result in these losses and increase the partition or adsorption of hydrocarbon organic compounds (HOCs) in the rock-water system. The adsorptive behaviour of Aerosol-OT was studied under high salt concentration at room temperature in the presence of sandstone and shale. This study detected the adsorption based on the monitored changes in the initial concentration of the surfactant. The adsorption of the surfactant Aerosol-OT has been investigated using batch adsorption isotherms and the technique of UV-Vis spectroscopy. The objective of the study was to gain further insight into the surfactant adsorption for these adsorbents and to determine the appropriate isotherm model. The equilibrium results showed that the value of concentration changed from 0.03 g/L to the lowest value of 0.0124 g/L, which is lower than half. The batch adsorption isotherms that Aerosol-OT adsorption behaviour followed was found to fit Langmuir-Frandluich model.

Wettability Alteration of Dolomite Rock Using Nanofluids for Enhanced Oil Recovery

Wettability alteration of rock by surfactant has been considered as feasible method for recovery of oil reservoirs by modifying the wettability of rock surface from oil-wet to water-wet condition. The impact of surfactant can be enhanced by adding nanoparticles. Cationic surfactant performed well in carbonate rock by forming ion pairs between cationic head and acidic component of the crude. Meanwhile, nanoparticles will form continuous wedge film between the liquid and solid surface. In this paper, Al2O3 and ZrO2 nanoparticles were used as enhanced oil recovery (EOR) agents. The impact of these two nanoparticles on contact angle and interfacial tension was studied. Besides that, adsorption Cetyltrimethylammonium Bromide (CTAB) surfactant on rock surface was also investigated. The results show a significant change in water-oil contact angle after application of surfactant and nanoparticles. Initial water-oil contact angle for 6 dolomites demonstrate oil-wet condition. Then, the dolomites were submerged in prepared solution for 48 hours. The result shows that, dolomites 2, 5 and 6 changes drastically to more water-wet condition with contact angle 56°, 40° and 47° respectively. For surfactant adsorption, the adsorption is very fast at the beginning. The adsorption rate after 5 minutes was 50 mg/g and after 60 minutes the adsorption rate was 310 mg/g. The adsorption rate slowed down after 60 minutes and after 180 minutes the adsorption rate was 315 mg/g in which the rate of adsorption achieve equilibrium. Nanoparticles retention test and Zeta potential shows that Al2O3 is more stable than ZrO2. The results for interfacial tension (IFT) also show a significant reduction. The IFT value reduces from 8.46 mN/m to 1.65 mN/m and 1.85 mN/m after the application of Al2O3 and ZrO2 nanofluids respectively

Nanoparticles Performance as Fluid Loss Additives in Water Based Drilling Fluids

Nanoparticles are used to study the rheological characteristics of drilling fluids. Nanoparticles have high surface to volume ratio, therefore only small quantity is required to blend in the drilling fluid. This research evaluates the performance of nanosilica and multi walled carbon nanotubes (MWCNT) as fluid loss additives in water based drilling fluid with various nanoparticles concentration and temperature. The results show that plastic viscosity, yield point and gel strength of drilling fluid increases as the concentration of nanoparticles increased. Drilling fluid with nanosilica gives the highest filtrate loss of 12 ml and mudcake thickness of 10 inch at 1 g concentration at 300°F. However, drilling fluid with MWCNT shows a decreasing trend in fluid loss and mudcake thickness. The results also show that xanthan gum containing 1 g of MWCNT gives 4.9 ml fluid loss and mudcake thickness of 4 inch at 200°F. After aging, plastic viscosity, yield point and gel strength of mud containing nanoparticles decrease significantly especially for 1 g of nanosilica and 0.01 g MWCNT. Fluid loss and mudcake thickness increased when the mud is exposed to temperature above 250°F. The results showed that xanthan gum with MWCNT gives a better rheological performance.

Reservoir Monitoring Using Streaming Potential; Is the Thermoelectric Correction Necessary?

Wellbore streaming current and their applicability in the location of subsurface sand bodies were discovered in 1931 and the usefulness of this measurement has persisted to the present day. Through the endeavor of many researchers, knowledge and understanding of streaming potential (SP) have slowly evolved from the original mere recognition of its existence to its present-day quantitative use in many applications such as Enhanced Oil Recovery (EOR), water flooding, intelligent wells, etc. The spontaneous potential acts to maintain overall electroneutrality when a separation of electrical charge occurs in response to gradients in pressure (Electrokinetic), chemical composition (Electrochemical), or temperature (Thermoelectric). In spite of it being discovered 70 years ago, unfortunately little work has been done to find measurable value especially for thermoelectric coupling coefficient. Many researchers attempt to generate a universal model for SP. They attributes the limitations (if any) of their model to the scarce availability of accurate estimation for coupling coefficient. This study measures the value of thermoelectric coupling coefficient for five rock samples saturated with 0.01M (NaCl) saline brine. The study takes account of temperature dependant electrode effect. The result shows value of 0.2 mV/K, which is in a good match with most of the published data. It was also found that there is no strong correlation between the thermoelectric coupling coefficient and porosity. The measured thermoelectric values are considered insignificantly small compared to the electrokinetic effect in the system.

Monitoring Water Alternate Gas (WAG) Process Using Streaming Potential Measurement

Spontaneous potential (SP) is commonly measured during reservoir characterization. SP signals are also generated during hydrocarbon production due to the streaming potential occurrence. Measurement of SP could be used to detect and monitor water encroaching on a well. SP signals could also be monitored during production, with pressure support provided by water alternate gas (WAG) process. The objectives of this study are to quantify the magnitude of the SP signal during production by WAG injection and to investigate the possibility of using SP measurements to monitor the sweep efficiency. Measurement of streaming potential has been previously proposed to detect the water encroachment towards a production well. The peak of the signal corresponds to the waterfront where there is a change of saturation from ionic water to non-polar hydrocarbon. Similar trend is predicted in the case of WAG where we have several interfaces between the injected water and the injected gas. The results indicate that the magnitude of the SP generated in hydrocarbon reservoir during WAG process can be large and peaks at the location of the moving water front. Gas, which can be assumed to be non-polar, exhibit no electrokinetic effect. These observations suggest that WAG displacement process can be monitored indirectly from the signal acquired. Water or gas override can be detected and controlled if wells were equipped with inflow-control valves. As a conclusion, the SP measurement is a promising method to monitor the effectiveness of a WAG process. This study is significant because monitoring the progress of water and gas in a WAG process is key in the effectiveness of this enhanced oil recovery method. Measurement of the streaming potential provides another method besides using tracers to monitor the WAG profile. Better monitoring will lead to more efficient displacement and great benefits in term of economy and environment.

Review: a New Prospect of Streaming Potential Measurement in Alkaline-surfactant-polymer Flooding

The synergy of alkaline, surfactant and polymer has revealed the potential of alkaline-surfactant-polymer (ASP) flooding as the most promising chemical Enhanced Oil Recovery (EOR) method. The synergistic interactions between the chemicals with reservoir rock and fluids could change the environment in porous media, which have potential effects on streaming potential measurement. Limited studies have been focused on the application of streaming potential in monitoring EOR processes, particularly ASP. This paper aims to propose the potential of streaming potential as a new prospect in monitoring ASP flooding by reviewing the streaming potential principles and associated ASP mechanisms. ASP mechanisms involve interfacial tension (IFT) reduction, mobility ratio improvement, and wettability alteration, which could enhance sweep efficiency and displacement process. The potential problem is the chemical losses due to polymer and surfactant adsorptions on the rock surfaces, but alkaline has significant advantage in reducing adsorption. The alteration of rock surface and fluid properties during ASP flooding could significantly affect streaming potential, which arises when the double layers exist with respect to the flow of excess charges in porous media. Streaming potential measurement should be further investigated to monitor the polymer and surfactant adsorption and ASP progression in porous media. Development of numerical model for the correlation would be a great advantage. The findings could provide new prospect in the correlation between streaming potential and ASP flooding, which could be a potential approach in monitoring the efficiency of the process during production.