No abstract

<em>Steamflood is the most successful thermal EOR applied throughout the world and have produced the biggest portion of oil from EOR methods. As high intensity energy and associated cost are put to produce oil, optimization in any level can have tremendous impacts. Optimization in steamflood operation can be achieved by optimizing steam injection (rate, time), especially in mature pattern/ field or nearing the end of field life/ abandonment. This objective can be done thru utilization of retained heat in the reservoir and overburden/ underburden as they are not instantaneously produced with fluids. By using reservoir simulation, it can be shown that injection is not necessary to be continue until abandonment but can be stopped at a much earlier time hence a much profitable steamflood operation can be achieved.</em>

Increasing concentrations of greenhouse gases (GHG), including CO2, will lead to changes in the Earth’s climate with the consequence of the rise in the global average temperature. Reducing CO2 atmospheric concentrations by capturing emissions at the source and then storing them in subsurface reservoirs is considered a reliable solution until emission-free energy sources are developed and viable. Depleted oil and gas reservoirs, saline water aquifer, un-mineable coals are common sites for underground storage. The injection of CO2 in coal beds, known as ECBM is considered one of the most efficient and favorable economic options of all storage because CO2 is stored and at the same time will improve the recovery of coal bed methane. This method has huge potential as Indonesia hosts many coal deposits, however, exploitation of CBM is still very limited and mostly on pilot project status. The objectives of this study are to realize the potential value of ECBM and understand important operating parameters that will optimize the project. Reservoir simulations are an inexpensive method for predicting optimal trade-offs between these two separated processes (maximum storage/sequestration and maximum CBM production). This study reveals that methane recovery dependent strongly on the injection rate, while coal swelling/shrinkage only affects early production.

In addition to extensive information that has been obtained from pre-feasibility, exploration, and drilling phase, we can improve our knowledge of reservoir behavior related to thermal extraction using sensitivity analysis. Such analysis is commonly applied to address technical uncertainty and risks in economic evaluation. The purpose of this study is to determine the parameters that have the most influence on thermal power generation using two different approaches named one-factor-at-a-time or OFAT and response surface method or RSM. Moreover, RSM analysis allowed us to make a predictive model for thermal power extracted in liquid-dominated geothermal reservoir. Literature study is conducted to understand various properties commonly encountered in a liquid-dominated geothermal reservoir including porosity, conductivity, reservoir temperature, and permeability. This information is then used to construct reservoir model in CMG STARS simulator with a single producer and injector. Two different sampling method, named OFAT and Box-Behnken are used to construct dataset, each contains different combination of levels of reservoir porosity, conductivity, temperature, permeability, and re-injection temperature. A total of 31 models using OFAT method with 7-level for each parameter are simulated to understand individual effect of each parameter. Meanwhile, 47 models are constructed using RSM method with 3-level for each parameter to evaluate the effect of interaction between parameters on thermal generation potential as well as constructing predictive model. Sensitivity analysis using both OFAT and RSM agree that the reservoir temperature is the most significant characteristic of geothermal reservoir to affect its thermal power potential. Meanwhile, re-injection temperature that initially expected to strongly effect the lifetime and sustainability of a liquid-dominated geothermal utilization is insignificant. This finding suggest that optimization re-injection temperature is solely for the purpose of maintaining sustainability of geothermal reservoir or cater the concern of environmental issue on wastewater management, and not for maximizing the thermal extraction.

<p><em>Foam injection is a variance of gas flood as tertiary recovery method designed to mitigate low sweep efficiency normally found in gas flood due to inheritance of density difference between injected gas and oil which often severed by presence of reservoir heterogeneity (permeability contrast in this case). Foam EOR has two goals: (1) improve oil recovery by promoting better sweep efficiency, and (2) reduce carbon emission related to global warming issue provided that the injectant gas used is CO2, hydrocarbon gas or flue gas.. Reservoir simulation performed is able to show recovery improvement of foam compared to continuous gas injection.</em></p>