Near Well Supercritical CO2 Injectivity Study in Depleted Clastic Gas Field in Offshore Malaysia

Abstract

Abstract PETRONAS is committed to reduce the bulk carbon dioxide (CO2) emission to the atmosphere by re-injecting the produced CO2 from high CO2 gas field to nearby identified storage site. One of the most important components to develop the storage site would be the understanding on the CO2 injectivity potential. Limited study is identified for near well CO2 injectivity research especially in determining the critical velocity rate to identify the injectivity potential during supercritical CO2 injection (scCO2). In this paper, the injection potential for Field D, which is in Offshore Malaysia has been studies for the storage prospect maturation purposes. Two representative sandstone samples with two distinctive permeability (~80 mD and ~300 mD) from the targeted injected zone in Field D were selected for the analysis. The initially brine saturated core sample was injected with scCO2 at fixed flowrate to establish the core at irreducible brine saturation. ScCO2 was then injected at slightly higher flowrate until the stable differential pressure is achieved. For each subsequent increases in flow rate, base rate of scCO2 is implied in the intervals to observe if there is any formation damage occurred in laminar flow regime. Relative Injectivity Coefficient (RIC) was also calculated using the returned rate differential pressure information. Furthermore, pre- and post-injection core characterization, using routine core analysis (RCA) and X-Ray CT-scan were conducted to examine any petrophysical alteration that might take place during the experiment. The critical velocity rate is then analyzed according to the differential pressure data which later upscaled to well-scale resolution. Based on the differential pressure trend from the two injectivity experiments, there is no clear evidence of formation damage even after the core has been subjected to high scCO2 lab flowrate (~110 cc/min). Only minor dissolution and fines flush-out was occurred. This observation is confirmed by pre- and post-scCO2 injectivity analyses comparison where the petrophysical changes is very minimal. Based on the evidence from differential pressure and pre- and post-sample characteristics, it can be concluded that the critical flow rates were higher than the maximum achievable laboratory flow rates. This denotes that there is no injectivity issues that is expected to occur up to upscaled well flowrate of 18.5 MMscf/day during the CO2 injection in storage target zone in Field D.