In recent years, Carbon Capture and Storage (Sequestration) (CCS) has been proposed as a potential method to allow the continued use of fossil-fuelled power stations whilst preventing emissions of CO2 from reaching the atmosphere. Gas, coal (and biomass)-fired power stations can respond to changes in demand more readily than many other sources of electricity production, hence the importance of retaining them as an option in the energy mix. Here, we review the leading CO2 capture technologies, available in the short and long term, and their technological maturity, before discussing CO2 transport and storage. Current pilot plants and demonstrations are highlighted, as is the importance of optimising the CCS system as a whole. Other topics briefly discussed include the viability of both the capture of CO2 from the air and CO2 reutilisation as climate change mitigation strategies. Finally, we discuss the economic and legal aspects of CCS.

Carbon capture and storage update

The flow of homogeneous fluids through porous media: analogies with other physical problems

With the decline in oil discoveries during the last decades it is believed that EOR technologies will play a key role to meet the energy demand in years to come. This paper presents a comprehensive review of EOR status and opportunities to increase final recovery factors in reservoirs ranging from extra heavy oil to gas condensate. Specifically, the paper discusses EOR status and opportunities organized by reservoir lithology (sandstone and carbonates formations and turbiditic reservoirs to a lesser extent) and offshore and onshore fields. Risk and rewards of EOR methods including growing trends in recent years such as CO2 injection, high pressure air injection (HPAI) and chemical flooding are addressed including a brief overview of CO2-EOR project economics.

Enhanced Oil Recovery: An Update Review

The Intergovernmental Panel on Climate Change assumes the warming of the climate system, associating the increase of global average temperature to the observed increase of the anthropogenic greenhouse gas (GHG) concentrations in the atmosphere. Carbon dioxide (CO 2 ) is considered the most important GHG, due to the dependence of world economies on fossil fuels, since their combustion processes are the most important sources of this gas. CO 2 concentrations are increasing in the last decades mainly due to the increase of anthropogenic emissions. The processes involving CO 2 capture and storage is gaining attention on the scientific community as an alternative for decreasing CO 2 emission, reducing its concentration in ambient air. However, several technological, economical and environmental issues as well as safety problems remain to be solved, such as the following needs: increase of CO 2 capture efficiency, reduction of process costs, and verification of environmental sustainability of CO 2 storage. This paper aims to review the recent developments (from 2006 until now) on the carbon capture and storage (CCS) methodologies. Special attention was focused on the basic findings achieved in CCS operational projects.

Recent developments on carbon capture and storage: An overview

The rate of natural carbonation of tectonically exposed mantle peridotite during weathering and low-temperature alteration can be enhanced to develop a significant sink for atmospheric CO2. Natural carbonation of peridotite in the Samail ophiolite, an uplifted slice of oceanic crust and upper mantle in the Sultanate of Oman, is surprisingly rapid. Carbonate veins in mantle peridotite in Oman have an average 14C age of ≈26,000 years, and are not 30–95 million years old as previously believed. These data and reconnaissance mapping show that ≈104 to 105 tons per year of atmospheric CO2 are converted to solid carbonate minerals via peridotite weathering in Oman. Peridotite carbonation can be accelerated via drilling, hydraulic fracture, input of purified CO2 at elevated pressure, and, in particular, increased temperature at depth. After an initial heating step, CO2 pumped at 25 or 30 °C can be heated by exothermic carbonation reactions that sustain high temperature and rapid reaction rates at depth with little expenditure of energy. In situ carbonation of peridotite could consume >1 billion tons of CO2 per year in Oman alone, affording a low-cost, safe, and permanent method to capture and store atmospheric CO2.

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In situ carbonation of peridotite for CO2 storage

Eleven hydraulic fracture treatments were performed in deep (3300 to 3800 m (10,830 to 12,470 ft)), extremely high-temperature (180 to 195{degrees}C (356 to 383{degrees}F)), naturally fissured, gas-condensate reservoirs. Formation permeabilities at the fractured-well locations range from 0.003 to 0.2 md, while the initial formation pressure gradient is about 0.13 bar/m (0.57 psi/ft). The producing fluid is high-gravity gas (0.83 to 1.15 to air) and contains up to 22% CO{sub 2} and up to 4% H{sub 2}S. Job sizes have ranged from 300 to 2000 m{sup 3} (80,000 to 528,400 gal) of fluid and 50 to 600 Mg (110,130 to 1,321,590 lbm) of high-strength proppant. This paper emphasizes the general approach to well completion and stimulation treatment design, treatment execution, and evaluation. Interesting items include the engineering of the fracturing fluids to sustain their viscosity at the extreme temperatures and to reduce leakoff in these highly fissured formations. An outline of the reservoir description is also given. Post-treatment well production has been excellent in most cases. Well PI's increased from 0.01 to 0.6 m{sup 3}/d {center dot} bar{sup 2} (0.0017 to 0.1 scf/D-psi{sup 2}) to 0.235 to 7.83 m{sup 3}/d {center dot} bar{sup 2} (0.04 to 1.3 scf/D-psi{sup 2}). Treatment resultsmore » suggest that leakoff can be controlled with particulate agents, that delayed crosslinking is the only way to execute these treatments, and that hydraulic fracturing can greatly improve the production from naturally fissured formations. Fracture design and the predicted well production are compared with post-treatment performances in selected wells.« less

Fracturing of High-Temperature, Naturally Fissured, Gas-Condensate Reservoirs

Inflow Performance for a Hydraulic Fracture in a Deviated Well

Recipe for Success in Ultradeep Water

Underground natural gas storage has been used extensively in countries with large natural gas demand. Although much of the storage and withdrawal have been associated with seasonality, storage is becoming essential in an integrated natural gas management. It is particularly important in large operations, such as liquefied natural gas (LNG), where the total production rate must be maintained irrespective of the producing field day-to-day capacity. Natural gas storage capacity is affected by reservoir volume and tolerable pressure (to avoid fracturing) and injection or production rates that are affected by reservoir permeability, natural reservoir drive mechanism, well completion/stimulation, and the impact of cyclical losses.
We present here a new sequence of calculations and estimations demonstrating salient elements of this practice: • Maximum capacity estimation with a new type of graphical construction, blending concepts of the classical p/Z vs. cumulative recovery straight line in natural gas production.
• Prediction of withdrawal rates and time, constrained by decreasing storage pressure.
• Determination of maximum or sustainable withdrawal rate for a period of time. In all cases, the injecting and
producing wells are hydraulically fractured. The hydraulic fractures are designed for the withdrawal rate. Thus,
the required number of wells is determined.
These concepts are applied to a depleted natural gas field with an average pay of 33 ft and a permeability of 45 md. Forecasts of injection or production rates, cumulative storage or withdrawal, and pressure buildup or decline are presented as functions of time. The purpose of this case study is to sustain an LNG liquefaction operation for a specified period of time by employing underground natural gas storage.

Michael J. Economides

Papers

Fracturing of High-Temperature, Naturally Fissured, Gas-Condensate Reservoirs

Inflow Performance for a Hydraulic Fracture in a Deviated Well

Recipe for Success in Ultradeep Water

The Role of Underground Storage in Large Natural Gas Production Operation

Flaws in Fracture Designs: A Continuing Problem