Insights and Commentaries
Advances in CCS monitoring featured in new video online
15th May 2015
Topic(s): Carbon capture, Engineering and project delivery, use and storage (CCUS)
This insight, co-written by John Hamling, Senior Research Manager of the Energy and Environmental Research Center at the University of North Dakota, and Neil Wildgust, the Global CCS Institute’s Principal Manager – Storage, outlines how the installation of a casing-conveyed permanent downhole monitoring (PDM) system can be used to monitor, measure and verify the geological sequestration of carbon dioxide.
The Energy and Environmental Research Center (EERC), based in Grand Forks, North Dakota, has created a video presentation to highlight the installation and application of a casing-conveyed permanent downhole monitoring (PDM) system. This emerging technology promises to deliver improved performance monitoring of carbon dioxide (CO2) geological storage sites.
Monitoring, measurement, and verification (MMV) programs are the component of a carbon capture and storage (CCS) project that tracks and verifies CO2 injected into a geologic storage reservoir. A key parameter of many MMV strategies is access to accurate and reliable measurements of pressure and temperature within the subsurface. Such data can be used by reservoir engineers, geologists, and project managers for a number of purposes including:
- To ensure that injection rates and pressures are maintained within specific limits (agreed upon with the regulatory body) for each storage site to avoid damage to the reservoir, overlying sealing layer (“caprock”), or wellbore.
- To enable assessments of storage performance to:
- Allow accurate calibration of predictive models;
- Identify changes in injectivity;
- Monitor for indications of out-of-zone fluid migration;
- Assess compartmentalization of storage reservoir;
- Characterize fluid phase behavior;
- Evaluate wellbore integrity; and
- Correlate reservoir conditions with monitoring at the wellhead.
- In the case of CO2 injection for enhanced oil recovery (CO2-EOR), pressure data can be used to ensure that miscible conditions are maintained in the reservoir to maximize oil production.
Sensors placed in the subsurface provide accurate pressure and temperature measurements of the formation being monitored. Deep wells, such as those employed for injection into, or monitoring of, geological storage reservoirs use steel casings to shield the well from surrounding rock formations and fluids – typically along the entire length of the well. The PDM system, as deployed by the EERC, uses a series of sensors attached to the outside of the casing to directly measure pressures and temperatures within the reservoir and overlying formations. The sensors are connected to the surface via a series of armoured cables, which provide pressure and temperature data to a data logger or directly to an operator via wireless signals. This system can be engineered to accommodate a variety of well completions and does not impact injection or production operations.
PDM installation can also include other measurement systems to enhance monitoring capabilities. For example, the EERC also deployed a distributed temperature system (DTS), which consisted of a fiber optic line running along the entire length of the casing. DTS was able to gather temperature data at 1m intervals, effectively providing a temperature profile for the entire well.
The benefits provided by installation of a PDM system are numerous. Pressure and temperature data can be provided on a continuous, real-time basis – and where relevant, integrated into automated intelligent control systems for injection, production, and other field management activities. Moreover, sensors can be installed at any position on the casing to allow monitoring of multiple reservoir zones, or where applicable above or below the reservoir. This is of particular relevance to geological CO2 storage. For example, monitoring above the reservoir can provide direct assurance of effective reservoir containment by demonstrating the absence of fluid or pressure communication between the reservoir and overlying strata. Demonstrating secure containment of injected CO2 is a key requirement for complying with emerging storage regulations and providing stakeholder confidence in CCS as an effective strategy for mitigating greenhouse gas emissions.
Installation of a PDM system does require additional hardware, engineering design and operational considerations, which come at an incremental cost. Specific deployment requirements include modified wellheads, specialized equipment, customized casing joints and precise well logging and depth control. However, the long term cost benefits achieved through enhanced monitoring and improved reservoir engineering can, in many cases, provide long-term value.
The 20-minute video presentation titled “Installing a Casing-Conveyed Permanent Downhole Monitoring System” is intended to acquaint a technical audience with the basics of casing-conveyed PDM systems and the unique field installation practices that these systems require, using an example from a CO2-EOR project in the Denbury Resources-operated Bell Creek oil field in southeastern Montana.
The video is a co-production of the Plains CO2 Reduction (PCOR) Partnership in collaboration with Prairie Public Broadcasting, Fargo, North Dakota. Funding is provided by the US Department of Energy’s Office of Fossil Energy and implemented through the National Energy Technology Laboratory, the PCOR Partnership members, and the members of Prairie Public.