Stress, pore pressure, and dynamically constrained hydrocarbon columns in the South Eugene Island 330 field, northern Gulf of Mexico

Hydrocarbon phase pressures at the peak of two severely overpressured reser voirs in the South Eugene Island 330 field, Gulf of Mexico, converge on the minimum principal stress of the top seal. We interpret that the system is dynamically constrained by the stress field present through either fault sl ip or hydraulic fracturing. In two fault blocks of a shallower, moderately overpressured reservoir sand, hydrocarbon phase pressures are within a rang e of critical pore pressure values for slip to occur on the bounding growth faults. We interpret that pore pressures in this system are also dynamical ly controlled. We introduce a dynamic capacity model to describe a critical reservoir pore pressure value that corresponds to either the sealing capac ity of the fault against which the sand abuts or the pressure required to h ydraulically fracture the overlying shale or fault. This critical pore pres sure is a function of the state of stress in the overlying shale and the po re pressure in the sand. We require that the reservoir pore pressure at the top of the structure be greater than in the overlying shale. The four rema ining reservoirs studied in the field exhibit reservoir pressures well belo w critical values for dynamic failure and are, therefore, considered static . All reservoirs that are dynamically constrained are characterized by shor t oil columns, whereas the reservoirs having static conditions have very lo ng gas and oil columns.