Suat Bagci

EFFECT OF BRINE COMPOSITION ON OIL RECOVERY BY WATERFLOODING

In this study, the effect of brine composition on oil recovery by waterflooding was experimentally studied. Different compositions of brine were injected in to packed one-dimensional unconsolidated limestone with Garzan crude oil (26° API) and distilled water. Ten different brine compositions, three brine mixtures are prepared and distilled water was used for injection throughout the study. The highest recovery 18.8% higher than distilled water injection) considering all the experiments was obtained by the injection of 2% KCl + 2% NaCl brine mixture.

A laboratory study of single-well steam-assisted gravity drainage process

Abstract An investigation of the optimization of startup procedure for single-well steam-assisted gravity drainage (SW-SAGD) was made as the project economics are influenced significantly by the early production response. An experimental investigation of two early-time processes namely cyclic steam injection and steam circulation to improve reservoir heating is discussed and compared to continuous steam injection as well as other well configurations like vertical injector–horizontal producer and horizontal injector–horizontal producer. Crushed limestone saturated with heavy oil (12.8° API) and water was packed in a laboratory model for the experiments. The effectiveness of the methods is compared within themselves and to conventional steam-assisted gravity drainage (SAGD) by measuring the size of the steam chamber as a function of time. The steam chamber area for cyclic steam injection is slightly greater than that of steam circulation case. Furthermore, numerical simulation studies of different early-time processes were conducted and compared to the experimental data using a commercial simulator. It was observed that the numerical model results underestimated the cumulative oil recovery and the steam chamber size. Results from this study, including cumulative recoveries, temperature distributions, and production rates display the differences between the methods.

In-situ combustion laboratory studies of Turkish heavy oil reservoirs

Abstract The purpose of this research was to perform dry and wet forward combustion experiments for Turkish heavy oil reservoirs (Raman, Adiyaman and Camurlu and Bati Kozluca) under different experimental conditions. In the experiments, a vertical tube was packed with crushed limestone and saturated with crude oil and water. It was observed that peak temperatures were higher when stabilized combustion was achieved and decreased as the combustion front approached the outlet end of the tube. In wet combustion experiments, the rate of combustion reaction and therefore rate of heat generation were reduced with the resultant drop in peak temperatures. In dry and wet combustion experiments, excess carbon-dioxide productions were observed due to the decomposition of carbonate minerals. Atomic H/C ratio of the fuel consumed decreased as the average peak temperature increased. Fuel consumption rate was higher for dry combustion experiments as the °API gravity of the crude oils increased. A decrease is also observed in fuel consumption rate after the water–air ratio value is reached to optimum value. For high water–air ratio in wet combustion experiments, a general decrease was observed as the °API gravity of the crude oils increased.

Determination of formation damage in limestone reservoirs and its effect on production

Abstract Reduction of injectivity of wells by formation damage can be of considerable magnitude during waterflooding of oil reservoirs. Variation of pH of the flowing fluid is an indicator of chemical activity occurring in the formation. High pH promotes formation damage by particle deposition within the porous media and consequently particle bridging at the pore throats. Permeability reduction is used as quantitative measure of formation damage. In this paper, the results of core flow experiments in limestone formations are presented. Effluent pH and Cl concentrations are measured at the outlet of the porous medium. Brines are prepared with sodium, calcium and potassium salts (NaCl, CaCl2, KCl). In limestone formations, formation water, which is used in injection, and artificially prepared brine in various concentrations, caused the permeability reduction. High pH values in produced water caused the permeability reduction and consequently the pores are plugged and formation damage is observed. In alkaline flooding experiments, permeability reduction is observed as a result of high pH alkaline fluids. The permeability reduction is minimized using brines of NaCl, CaCl2 and KCl mixtures and high oil recoveries are obtained. Suspended solid particles are released and moved with injection water when salt concentration drops below the critical salt concentration, causing the permeability reduction and formation damage. Experiments below the critical salt concentrations, resulted in a reduction in permeability values in consolidated/unconsolidated limestone samples, whereas, high pH value solutions caused a reduction in permeability values, plugged the pores and resulted in formation damage.

Oxidation of Heavy Oil and Their SARA Fractions: Its Role in Modeling In-Situ Combustion

In situ combustion is a thermal recovery technique where energy is generated by a combustion front that is propagated along the reservoir by air injection. Most of the previously conducted studies report thermal and fluid dynamics aspects of the process. Modeling in situ combustion process requires extensive knowledge of reservoir data as well as reaction kinetics data. Unfortunately, limited kinetic data are available on the rates and the nature of partial oxidation reactions and the high-temperature combustion reactions of crude oils and their saturate, aromatic, resin, and asphaltene (SARA) fractions. Moreover, the impact of such data on the modeling of the in situ combustion process has not been investigated thoroughly. Thus, we modeled in situ combustion experiments conducted on a 3D semi-scaled physical model that represents one fourth of a repeated five spot pattern. In all experiments a vertical injector is employed whereas, both vertical and horizontal producers have been installed to recover two different crude oils (heavy and medium). Several locations for the producers have been tried while keeping the length of the wells constant: vertical injector-vertical producer, vertical injector-horizontal side producer, and vertical injector-horizontal diagonal producer. In these experiments diagonal producers performed better than the others. We first simulated the experiments by incorporating a kinetic model that is based on grouping the products of cracking into six pseudo components as heavy oil, medium oil, light oil, two non-condensable gases and coke using a commercial thermal simulator (CMGs STARS) Four chemical reactions were considered: cracking of heavy oil to light oil and coke, heavy oil burning, light oil burning, and coke burning. Most of the experiments were history matched successfully with the exception of ones where a diagonal horizontal producer was used. We then repeated the simulations using SARA kinetic parameters. We observed that all matches were somewhat improved. We finally present a discussion of application of the models to field scale.

The effects of metallic catalysts on light crude oil oxidation in limestone medium

Abstract In this study, 28 experiments were performed to study the effects of metallic additives on light crude oil oxidation in limestone medium. Karakus and Beykan crude oils from Turkish oil fields were used. The metallic additives were ferric chloride (FeCl 3 ), copper chloride (CuCl) and magnesium chloride (MgCl 2 ·6H 2 O). The mixture of aqueous solutions of three metallic salts with limestone and the crude oils was subjected to a controlled heating schedule under a constant flow rate of air. The produced gas was analysed for its oxygen and carbon oxides contents. The results of reaction kinetics showed that the molar CO 2 /CO ratio values of fuel combustion increased when additives were added. A decrease in the atomic H/C ratio with an increase in temperature was observed for all runs. The reaction order, m in Arrhenius equation increases as concentration of copper and magnesium chloride additive increases but decreases as ferric chloride additive increases in both crude oils. It is observed that the metallic additives except ferric chloride decreased the Arrhenius constant, Ar, for both crude oils. As concentration of ferric chloride increases the activation energy of Karakus crude oil increases while activation energy of Beykan crude oil decreases. The copper chloride additive shows same trend for both crude oils. The 1.0 mol% concentration decreases the activation energies. The 2.0 mol% magnesium chloride increases the activation energy of Karakus crude oil while decreases the activation energy of Beykan crude oil more than 1.0 mol% does. For Karakus crude oil, the oxygen consumption curves of 2.0 mol% of metallic additives show one peak. There is similar behavior between runs with 1.0 mol% of ferric chloride and magnesium chloride and runs with no additive, but the oxidation reaction peaks with metallic salts at both concentrations occurs at lower temperatures. For Beykan crude oil, all the additives lower the peak temperature when they are compared to standard run. The trends of the curves are actually the same. Copper chloride shows one peak with the 1.0 and 2.0 mol% runs for both crude oils.

Improved oil recovery using alkaline solutions in limestone medium

Abstract In this study, the effect of sodium hydroxide (NaOH) and sodium silicate (NaSiO 4 ) solutions for the improved oil recovery of Garzan (26 API°) and Raman (17.2 API°) crude oils with variable salinity of the alkaline solutions, and the effect of injection flow rate at the salinity values of the alkaline solutions that yielded maximum oil recovery for both crude oils has been investigated using a one-dimensional unconsolidated limestone reservoir model. As the previous study, the interfacial tension measurements of the given crude oils and alkaline solutions interface have been measured to find the optimum concentrations of the alkaline that give the minimum interfacial tension at the crude oil/alkaline solution interface, at different salinity of the alkaline solutions. Using these optimum alkaline concentrations, 22 displacement runs have been performed; 13 runs with the variable salinity of the alkaline solutions, six runs with the variable injection flow rate, and the remaining three runs were the base floods, performed without oil to see the interaction of alkaline solutions with the porous matrix. The results of the displacement tests showed that the NaOH solutions with increasing salinity, has given the most significant incremental oil recovery, about 3–9% for Garzan crude oil, while the NaOH and NaSiO 4 solutions with different salinity did not produced any significant incremental oil recovery for Raman crude oil, when compared with the base waterfloods performed for each crude oil types. Six displacement runs have been performed; three runs for Garzan crude oil and three runs for Raman crude oil at injection flow rates of 400, 300, 200 and 100 cm 3 /h for each crude oil with the salinity of the alkaline solution that yielded maximum oil recovery. The results of the displacement tests showed that injection flow rate of alkaline solution has an important effect on Garzan crude oil and has less effect on Raman crude oil in the scope of oil recovery achieved. The optimum injection flow rates for both Garzan and Raman crude oils have been found, which was 200 cm 3 /h for Garzan crude oil and 300 cm 3 /h for Raman crude oil for our model.

Effect of Clay Content on Combustion Reaction Parameters

The role of clay in reservoirs and its possible influence on kinetics of crude oil burning is not entirely clear. However, it is known that (1) clay fractions of the reservoir matrix possess the highest surface area per gram, (2) clay fractions are the most chemically reactive of the inorganic constituents present in the reservoir, and (3) clay minerals generally possess catalytic properties toward various organic liquids. This study was aimed to investigate the role of clay on thermo-oxidative behavior of crude oil at different clay contents in limestone medium. To do this, non-isothermal kinetic experiments were conducted in a reaction cell by injecting 1.5 lt/min of air into the cell having matrix containing limestone (92% calcite, 6.6% dolomite and 1.4% quartz) with 0, 5 and 10% addition of clay (kaolin). The pre-combustion and combustion behavior of Batı Raman (12.9° API gravity) crude oil from south-east Turkey was studied by using continuous analysis of produced gases. Clay content of the matrix influenced the amount of the fuel deposited on the limestone. More fuel was increasingly deposited as the clay content was increased. Addition of clay also increased the combustion peak temperature. This can be attributed to the (1) or (3) of the preceding section. Results also indicate that the average molar CO 2 /CO ratio increased from 3.71 to 5.97 upon addition of 10% clay to the limestone. Finally, a uniform trend of decreasing activation energies as well as the Arrhenius constants by addition of clay to the limestone was observed. It was concluded that clays large surface area affects the values of Arrhenius constant, while it is the catalytic properties of clay that lower the activation energies of all three major reactions (i.e., low temperature oxidation, fuel deposition and fuel combustion) involved in the in-situ combustion process.

Oxidation kinetics of a Turkish oil shale

Abstract Oxidation kinetics of a Turkish oil shale (Bolu-Himmetoglu), when subjected to an air flow of 1.5 L/min at different pressures, was studied. CO, CO 2 and O 2 gas concentrations were measured as a function of controlled increasing temperature. The reaction rate equation obtained at the end of the kinetics study showed that oxidation of oil shale is dependent upon oxygen partial pressure and organic matter content, and that the relation between reaction rate constant and temperature fits an Arrhenius type of equation. The oxidation reaction was determined to occur in three stages; low temperature, transition and high temperature zones. The rate controlling mechanism was observed to be chemical kinetics in the first region, while diffusion was rate controlling in the last stage of the reaction.

Effect of Pressure on Combustion Kinetics of Heavy Oils

In this study, 16 experiments were conducted to study the effects of pressure on crude oil oxidation in limestone medium. Karakus (29°API), Beykan (32°API), Bati Raman (12°API), Camurlu (12°API), Adiyaman (26°API), Garzan (28°API) and Raman (18°API) crude oil from Turkish oil fields were used. The mixture of limestone and the crude oil was subjected to a controlled heating schedule under a constant flow rate of air. The produced gas was analyzed for its oxygen and carbon oxides contents. The results of reaction kinetics showed that the molar CO2/CO ratio values of fuel combustion increased with increasing pressure. A decrease in the atomic H/C ratio with an increase in temperature was observed for all runs. Results indicate that oxygen consumed increases with increasing operating pressure. This means more fuel is burnt by increasing the pressure, which is due to the effect of pressure on the volatility of the oil components. Because increasing pressure will depress oil volatility, the fuel availability would increase. This also suggests that distillation might be the dominant mechanism for fuel deposition. A trend of increase in activation energy values by increasing pressure is observed.