Casing influence in reservoir compaction measurement by radioactive markers in the Northern Adriatic, Italy.

The reliability of in situ compaction measurements made in producing gas/oil reservoirs with the aid of the radioactive marker technique (RMT) is a very important issue as an essential parameter controlling the geomechanical response of fluid extraction from the subsurface, i.e., the rock vertical compressibility cM, is obtained from RMT data. The validity of cM as provided by RMT has recently been questioned on the basis of the possible disturbance that a fully cased hole can induce on the actual reservoir compaction. By the use of a numerical approach and real casing information, the present paper addresses and discusses the reliability of RMT measurements performed in hole casings of the Northern Adriatic gas fields, Italy. The results show that the casing stiffness affects the RMT measurements only marginally, and especially so at a larger depth (i.e., 3,000 m), and does not significantly impact on the estimate of cM derived from RMT data.