CASE STUDY OF THE EFFECT OF ROCK MINERALOGY ON ANIONIC SURFACTANTS INJECTION IN THE SANDSTONE RESERVOIR OF THE AIRBENAKAT FORMATION

• Main Author: Idea, Kharisma
• Format: Dissertations
• Language: Indonesia
• Subjects: Pertambangan dan operasi berkaitan
• Online Access: https://digilib.itb.ac.id/gdl/view/66307
• Institution: Institut Teknologi Bandung

In chemical injection research, Berea has been used for 30 years as an injection medium. The use of Berea is recommended because it represents a good sandstone reservoir with porosity ranging from 10-25% and permeability 50-1000 mD. The increase in oil recovery produced is very good if chemical injection is carried out using Berea. The problem was found when the same injection method was applied to a sandstone reservoir sample in Indonesia, in the Airbenakat Formation. With the same range of porosity and permeability between reservoir samples in the Airbenakat and Berea Formation, the results of increasing oil recovery after water injection were different. From the results of research using anionic surfactants on Berea and reservoir samples, it was found that the increase in oil recovery with Berea reached 50% after water injection and the increase in oil recovery in reservoir samples was below 10%. The sandstone of the Airbenakat Formation is Graywacke where the grains consist of quartz and felspar, cement consists of calcite and clay. Clay can be present as a matrix in Graywacke sandstones. Analysis of outcrop and reservoir sandstones was carried out to identify the presence of calcite and smectite (montmorillonite) minerals by performing X-Ray diffraction (XRD), thin section analysis, Scanning Electron Microscope-Energy Dispersive X-Ray (SEM-EDS). This study was conducted to determine the effect of calcite and smectite (montmorillonite) on the success of anionic surfactant injection. The anionic surfactant used is alkyl carboxylate. The characterization and performance of the surfactants were evaluated through measurements of Critical Misselle Concentration/CMC, Interfacial-Tension/IFT, Contact Angle and Adsorption. The test results show the influence of minerals such as smectite (montmorillonite) and carbonate cement (calcite) on the performance of alkyl carboxylate surfactant solutions. Calcite and smectite have positive and negative surface charges which will affect the adsorption and/or deposition of anionic surfactants. Smectite mineral (montmorillonite) is very reactive to water, and causes swelling which results in the reduction of rock pore size and reduces permeability so that the surfactant injection results are not optimal. Calcite reacts with alkyl carboxylate anionic surfactants because of the surface charge in which anionic alkyl carboxylate surfactants are vi negatively charged while calcite minerals are positively charged. The interaction of anionic surfactant solutions with inorganic ions such as Ca2+ causes precipitation and at the injection scale can cause blockages in the sample pores so that the injection pressure becomes large. Adsorption and/or deposition affect the oil recovery after injection of surfactant solution in the sandstone outcrop and reservoir samples from the Airbenakat Formation, both positively and negatively. The content of calcite and smectite in the sandstone samples affected the increase in oil recovery after injection of anionic surfactants. The results of this study indicate that the high content of calcite and smectite inhibits the increase in oil recovery, and this negative effect reduces with the decrease in the content of calcite and smectite. The high content of calcite and smectite causes the adsorption of 2% A-127 surfactant solution to be high. Changes in the IFT value in the surfactant solution occurred from 10-3 mN/m to 100 mN/m for 48 hours indicating a decrease in the performance of alkyl carboxylate surfactant solutions. The high content of calcite causes the dissolution of calcite by anionic alkyl carboxylate surfactants as evidenced by an increase in the concentration of Ca2+ in the surfactant solution, both in the adsorbs test and coreflooding test. The dissolution of Ca2+ causes Ca2+ to migrate following the injection flow and increases the back-pressure to be higher during the injection process. The increase in oil recovery can still be observed in the sandstone samples which contain small amounts of calcite and smectite, depending on the amount of PV injection of the surfactant solution. The greater the PV injection of the surfactant solution, the higher the oil recovery.