Polymer Flooding in Artificial Hydrate Bearing Sediments for Methane Gas Recovery

Abstract

Polymer flooding has been one of the most promising methods used for enhanced oil recovery from matured crude oil reservoirs across the globe due to its distinct advantages over simple water flooding. However, the use of polymer flooding has not yet been investigated for methane recovery from hydrate reservoirs. In our earlier work, we have investigated the effect of various molecular weights and concentrations of polyethylene glycol (PEG) polymer on the phase stability and kinetics of methane hydrate. This information has been explored for successful use of PEG as a chemical agent for polymer flooding from hydrate reservoirs. In this work, detailed experimental investigations on methane production from hydrate bearing sediments have been carried out using PEG polymer flooding in a three-dimensional hydrate reactor. Initially, methane hydrate formation has been investigated using two silica sand porous beds (viz., 0.16 and 0.46 mm), and pure water at an initial hydrate formation pressure of 8 MPa and 277.15 K. Subsequently, hydrate dissociation studies have been carried out using polymer flooding at a final hydrate reservoir pressure of ∼4.3 MPa and 277.15 K. The effect of molecular weights (200 and 600 kg/kmol, viz., respectively), concentrations (0.2 and 0.4 mass fractions), and injection rates (1 and 5 mL/min) of PEG aqueous solution has been analyzed for methane gas recovery. PEG-200 is observed to be an effective flooding agent as compared to PEG-600 and other inhibitor such as ethylene glycol used in the literature. In addition, studies on the total dissolved solids (TDS) and electrical conductivity of PEG aqueous solutions have also been investigated before and after flooding to check the efficacy of polymer flooding for methane production. PEG has a much lower freezing point (208.15 K, i.e., −65 °C) compared to ethylene glycol (260.25 K, i.e., −12.9 °C); therefore, polymer flooding is expected to be more beneficial for methane gas production from hydrate bearing zones with low reservoir temperatures.

Phase Equilibrium of Methane Hydrate in Aqueous Solutions of Polyacrylamide, Xanthan Gum, and Guar Gum

“…This is the first study carried out to know the effect of the different molecular weights and concentrations of oilfield polymers on methane hydrate phase stability, and additional data has been generated to supplement the existing literature. Also, very recently, the studies on hydrate recoveries − are pitching up very fast, in which polymer and inhibitor injection can play a vital role and therefore the studies on oilfields polymers are highly recommended and useful.…”

Comprehensive Review on Exploration and Drilling Techniques for Natural Gas Hydrate Reservoirs

“…The most commonly used mud formulations in Gulf of Mexico, North Sea, and offshore Brazil are salt/polymer mud systems . The knowledge gained by testing different drilling fluids and inhibitors in hydrate sediments is as follows: (a) The commonly used drilling fluids in offshore deepwater drilling are NaCl/polymer formulations, KCL polymer solutions, sepiolite drilling fluid, and lecithin- and water-based drilling fluids. , (b) Widely used effective hydrate inhibitors are NaCl, KCl, and CaCl 2 . , (c) Ethylene glycol works best as a result of the fact that a higher number of hydroxyl groups are available to make hydrogen bonds with water, making it difficult for water to participate in the hydrate structure. , (d) The organic phase of the synthetic drilling fluid slightly suppresses the hydrate equilibrium temperature but increases the rate and amount of hydrate formation. This is due to the higher gas solubility .…”

Review on Enhanced Technology of Natural Gas Hydrate Recovery by Carbon Dioxide Replacement

“…Depressurization, − thermal stimulation, − and chemical inhibitor injection − are the most studied methods of gas hydrate production, which break down or change the phase equilibrium conditions of natural gas hydrate in the reservoir to decompose and produce natural gas. The chemical inhibitor injection method should not be used alone in hydrate exploitation because of its high cost, slowly action, and environmental pollution.…”