AAPG Southwest Section

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The great value of insoluble residue studies structure and stratigraphy on the lower Paleozoic of West Texas, especially the Ellenburger


An insoluble residue study can recognize formation tops and detailed depositional cycles within the Lower Paleozoic below the Woodford and Mississippian unconformities throughout the Permian Basin, Eastern Shelf, and Ft. Worth Basin area. Insoluble residue has been commonly used to pick the formation tops of the Lower Paleozoic from the Devonian through the Cambrian. The insoluble residue studies have been especially valuable and a most effective tool in determining true structure and stratigraphy within the Ellenburger dolomite throughout the Permian Basin, Eastern Shelf, and the flanks of the Ft Worth Basin.

Insoluble residues are the remains of limestone, and dolomite rocks after being acidized in hydrochloric acid for a period of time. Insoluble residue consists of the unacidized material after the carbonate is gone, such as sand, shale, minerals, chert types, quartz, siliceous fossils and allochems.

Insoluble residues can be used for many other evaluations in the Lower Paleozoic rock record. The insoluble residue is excellent for correlating subunits and cycles in the Lower Paleozoic, especially in the Ellenburger Formation. Insoluble residue can be used to subdivide the Lower Paleozoic stratigraphy into formations and fourth and fifth order depositional cycles.