Overpressure in Shale Gas

Abstract

Abstract A study of up to 2.5 km (8000 ft) of gas-bearing shale has shed new light on the relationship between geochemistry and overpressure. Our analysis of a few large geochemical data sets has also identified alternative ways to look at down-hole pressures and has revealed some limitations of currently available tools, such as Rock-Eval pyrolysis below a certain depth in Alberta and Quebec. The very thick Ordovician Shale of the St. Laurence Lowlands in Quebec is gas-bearing and prospective. While the prime target is the carbonate-rich Utica Shale, the overlying and thick Lorraine Shale was also studied. Recent Quebec geochemical data from the St. Lawrence Lowlands was analyzed together with hydraulic fracture and reservoir pressure data from the same wells. The first phase of the study focused exclusively on vertical wells and delivered new insights with respect to pressure domains and fracture gradients.