Depleted Oil and Gas Fields

Less commercially attractive, but still potentially important, is injection into oil and gas fields that are either close to exhaustion (so-called depleted fields) or have been abandoned as unprofitable. Once the oil or gas has been extracted, there remains a large volume of porous rock in which carbon dioxide can be retained. In this situation, there is no credit for enhanced fuel recovery but, because the formation has safely held oil/gas for geological periods of time, there is again confidence that the carbon dioxide will remain locked up indefinitely. It is necessary, however, to ensure that any holes in the caprock due to drilling and oil extraction have been permanently sealed before introducing the gas. 

---

Stevens S.H., Kuuskara V.A., et al. Sequestration of C02 in depleted oil and gas fields global capacity, costs and barriers. In Proceedings of Fifth International Con-... 

Storage in oil and gas fields Depleted oil and gas fields Enhanced oil or gas recovery... 

Gas storage in depleted oil and gas fields is the most world-wide used method and often the cheapest one. Most of these are depleted gas reservoirs, although a few depleted oil reservoirs are also operated for the purpose. The first gas storage experiment (injection) was made in a gas field in Welland County, Ontario (Canada) in 1915. The first gas storage facility in a depleted reservoir was built in 1916. 

The next-lowest-cost storage is likely to be at depleted oil and gas fields, where reservoir geology is already known, wells suitable for injection of C02 may have already been drilled, relevant permits may already exist, and subsurface rights may be well defined. 

Depleted oil and gas fields have a number of attractive features as geological repositories ... 

Geological storage is an obvious method for sequestration of carbon dioxide. The geological features being considered for carbon dioxide storage fall into three categories (1) deep saline formations, (2) depleted oil and gas fields, and (3) unmineable coal seams. 

Research on geosequestration is ongoing in several parts of the world. The main potential appears to be deep saline aquifers and depleted oil and gas fields. In both, the CO2 is expected to remain as a supercritical gas for thousands of years, with some dissolving. 

The demand for gas is highly seasonal. Thus pipeline companies economi2e by si2ing production faciUties to accommodate less than the system s maximum wintertime demand. Underground storage faciUties are used to meet seasonal and daily demand peaks. In North America, gas is stored in three main types of underground formations depleted oil or gas fields, aquifers that originally contained water, and caverns formed by salt domes or mines. 

Another plan is to pump the carbon into coal seams, old oil and gas fields and deep, porous rock formations. This high-pressure injection would also release the remaining oil or gas out of depleted fields. 

The storage of C02 in oil and gas fields has generally to be separated into storage in depleted reservoirs and storage in connection with enhanced recovery of hydrocarbons. Both options principally use the pore volume that previously had been filled with hydrocarbons or is to be depleted from hydrocarbons at the very moment of storage. 

CO2 may be able to be sequestered in geological formations, such as active and depleted oil and gas reservoirs, coalbeds, and deep saline aquifers. Such formations are widespread and have the potential to sequester large amounts of CO2 (Herzog et al., 2000). A model project is underway in the North Sea off the coast of Norway. The Sleipner offshore oil and natural gas field contains a gas mixture of natural gas and CO2 (9%). Because the Norwegian government taxes emissions of CO2... 

Depleted or nearly depleted oil and gas reservoirs may provide other geologic targets for long-term CO2 storage. Inactive fields could be reopened and used for direct storage projects. A concern is that old well bores may have not been sealed to present-day standards and may have degraded casing or well hardware left in place. Considerable evaluation would be required before they could be put into service. 

The depletion of easy oil and gas fields has led, in recent years, to the exploitation of both new deep reservoirs and already discovered fields that very often produce H S and COj at high temperature and pressure, showing, consequently, very severe corrosive conditions. Traditional completion type, i.e. carbon or low-alloy steels, associated with corrosion inhibitors, does not represent a rehable solution from the corrosion point of view. 

A considerable catalyst to the corrosion monitoring market has been expansion in the production of oil and gas, not only in the usual oil areas (US and the Middle East), but also the offshore developments in Europe. In addition to the usual uncertainty of the onset or progress of internal corrosion in the operation of plant, the oil industry has to face the considerable problem concerning prediction of field corrosivity and the possibility of the producing field becoming corrosive or more corrosive as depletion progresses. These factors have considerable influence on the installation of corrosion monitoring as oil and gas production is the major user of such equipment. 

Chemicals of various types are used in every stage of drilling, completing, and producing oil and gas wells. This review describes these chemicals, why they are used, and recent developments. These chemicals include common inorganic salts, transition metal compounds, common organic chemicals and solvents, water-soluble and oil-soluble polymers, and surfactants. As existing fields become depleted, use of chemistry to maintain production via well stimulation, more efficient secondary recovery operations, and enhanced oil recovery become ever more important. 

Recovery of CO2 in the oil and gas production is of major importance to promote enhanced oil recovery (FOR) from depleted fields High pressure CO2 is then pumped back into the reservoir at the periphery of the field and diffuses through the formation to drive residual oil toward the wells. The recycled gas generally needs to have a purity of at least 95 vol% CO2. 

Recovery of CO2 in the oil and gas production is of major importance to promote EOR from depleted fields ... 

---