TY - GEN

T1 - Formation mechanisms of cementation flaws in well cementations under consideration of paste rheology

AU - Kromer, Marco

AU - Haist, Michel

AU - Müller, Harald S.

PY - 2014

Y1 - 2014

N2 - The Carbon Capture and Storage (CCS) technology is internationally being discussed as a key element in reaching the CO2 emission goals within the next decade. Hereby the durable sealing of boreholes is of crucial importance to ensure safe operation and secure abandonment conditions. Besides the diffusivity and permeability of the hardened cement plug, a major leakage pathway results from cementation flaws. Within the presented research, the formation mechanism of cementation flaws will be investigated as a function of the rheological characteristics of the cement paste and drilling mud in combination with different borehole surfaces with defined roughness and lateral contractions and expansions. Therefore a test-setup was developed that can be used to simulate the last section of a borehole by scale 1 to 1. This borehole simulator consists of different cap rock replicas of cylindrical geometry which are hollow in the center forming an artificial borehole. The surface of this borehole can be designed to reproduce any desired surface roughness, with grooves ranging from approximately 1 mm up to several cm. These replicas are made of concrete and can be heated to defined conditions. Within the tests, the artificial borehole is filled with drilling mud, which is then displaced by a cement suspension being pumped in using the contractor technique. After hardening of the borehole cement, cylindrical sections of the cap-rock including the cementation can be mounted in an autoclave system in order to investigate the influence of cementation flaws on the tightness of the sealing. In a next step this large scale test-setup is scaled down by considering the relationships between the leading physical quantities. In doing so, the main rheological parameters for the formation of defects during the sealing of boreholes can be identified. Based on these experimental results an engineering model will be presented, which allows for the prediction ofthe leak quantity and borehole tightness as a function of the borehole geometry and the rheological properties of the cement paste.

AB - The Carbon Capture and Storage (CCS) technology is internationally being discussed as a key element in reaching the CO2 emission goals within the next decade. Hereby the durable sealing of boreholes is of crucial importance to ensure safe operation and secure abandonment conditions. Besides the diffusivity and permeability of the hardened cement plug, a major leakage pathway results from cementation flaws. Within the presented research, the formation mechanism of cementation flaws will be investigated as a function of the rheological characteristics of the cement paste and drilling mud in combination with different borehole surfaces with defined roughness and lateral contractions and expansions. Therefore a test-setup was developed that can be used to simulate the last section of a borehole by scale 1 to 1. This borehole simulator consists of different cap rock replicas of cylindrical geometry which are hollow in the center forming an artificial borehole. The surface of this borehole can be designed to reproduce any desired surface roughness, with grooves ranging from approximately 1 mm up to several cm. These replicas are made of concrete and can be heated to defined conditions. Within the tests, the artificial borehole is filled with drilling mud, which is then displaced by a cement suspension being pumped in using the contractor technique. After hardening of the borehole cement, cylindrical sections of the cap-rock including the cementation can be mounted in an autoclave system in order to investigate the influence of cementation flaws on the tightness of the sealing. In a next step this large scale test-setup is scaled down by considering the relationships between the leading physical quantities. In doing so, the main rheological parameters for the formation of defects during the sealing of boreholes can be identified. Based on these experimental results an engineering model will be presented, which allows for the prediction ofthe leak quantity and borehole tightness as a function of the borehole geometry and the rheological properties of the cement paste.

UR - http://www.scopus.com/inward/record.url?scp=85015369339&partnerID=8YFLogxK

M3 - Conference contribution

AN - SCOPUS:85015369339

T3 - Proceedings of the 10th fib International PhD Symposium in Civil Engineering

SP - 63

EP - 72

BT - Proceedings of the 10th fib International PhD Symposium in Civil Engineering

A2 - Rouleau, Nicolas

A2 - Bastien, Josee

A2 - Fiset, Mathieu

A2 - Thomassin, Mathieu

T2 - 10th International Federation for Structural Concrete (fib) International PhD Symposium in Civil Engineering 2014

Y2 - 21 July 2014 through 23 July 2014

ER -