POSAMENTIER, HENRY W., ARCO Exploration and Production Technology, Plano, TX; and GEORGE P. ALLEN, TOTAL Centre Scientifique et Technique, Paris, France
The transgressive systems tract (TST) is deposited during an interval characterized by landward migration of the shoreline and commonly overlies a progradational succession. During the time of transgression, sediments derived by transgressive erosion of the substrate are transported both landward as well as seaward and are deposited as backstepping barrier beach systems and healing phase deposits respectively.
The healing phase is defined as a wedge-shaped depositional unit comprising sediments that are deposited within the bathymetrically low area commonly occurring seaward of the last clinoform of an underlying "progradational phase." This wedge can approach thicknesses equivalent to that of the progradational phase. It is referred to as the healing phase because the area seaward of the relatively steeply dipping last clinoform of the progradational phase is progressively infilled or "healed over" as a morestable lower-gradient longitudinal equilibrium profile is re-established.
Based on well log and core data, the deposits of the healing phase consist commonly of sediments reworked from transgressed progradational-phase deposits, first by shoreface processes and subsequently by open-shelf wave processes. These sediments ultimately are deposited in deeper waters characterized by lower wave energy, which commonly occur seaward of the last progradational-phase clinoform. Based on seismic as well as well-log and core data, the strata that comprise the healing phase commonly are characterized by significantly lower gradients and have an onlapping relationship with the last clinoform of the subjacent progradational phase. Because of their onlapping relationship with the underlying progradational phase, these deposits can be readily mistaken for lowstand deposits. owever, healing-phase deposits typically are finer-grained than the deposits of the progradational phase and consequently contain inferior quality reservoir deposits.
AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.