Identification of Similar Intervals of Wells with Casing Failure and Coring Wells and the Determination of their Geomechanical Properties

To determine the static elastic parameters (SEP) (static elastic modulus and Poisson’s ratios) of rock in blocks with high casing damage rates and with limited core samples, an innovative technique has been proposed to identify similar intervals of wells with casing failure and coring wells and to determine the SEP of these intervals. First, the mechanical parameters of cores from coring intervals were tested, then the correlation between logging data and rock mechanical parameters between the similar intervals of the coring well and the casing failure well was analyzed, a model from combined modulus was established to determine static elastic parameters. Then a similar SEP identification criterion was proposed. Mechanical parameters of coring intervals were determined to establish correlations among the logging data and SEPs of rocks in these intervals. Eventually, models for the SEPs based on combined modulus were proposed. By studying correlation among the logging data acquired in the wells with casing failures and coring wells, criteria for similar intervals in wells with casing failure and cored wells were highlighted. By identifying intervals with similar properties in casing failure wells and cored wells, it is possible to determine SEP in intervals of casing failure. Testing and calculation results showed that the combined modulus and SEP with consideration of effective horizontal in-situ stresses may have correlations 10% and 20% higher than those from conventional calculation models. In general, identification criteria for similar intervals in casing failure wells and coring wells can be summarized as the highest correlation between acoustic travel time and GR, and minimum deviation among difference arrays in these two intervals. Research results showed that these techniques have relatively high applicability and accuracy in determination of SEP in multiple wells and intervals in areas with severe casing damage. Satisfactory performance has been observed in field applications of these techniques.