Study of Calcite Cement in Submarine Fan Complex in the Lower Cherry Canyon, Delaware Basin, TX

Chakraborty, Saswati

Calcite cement is found to be distributed throughout the reservoir quality sandstones in the South Wells Member of the Cherry Canyon Formation in the Ford Geraldine Field area, western Delaware Basin, along the Reeves-Culberson County line, Texas. Irregularly distributed calcite cement occurs in the form of tightly cemented zones with associated reduction in porosity. The volume of calcite cements therefore is probably the dominant control on heterogeneity in porosity and permeability. From four cored wells (~750 ft of core) and thin sections, there are four submarine channel complex intervals of sandstone are identified within the South Wells Member that are separated by thick (~15 to 18 ft) condensed sections of mudstone and associated siltstone.

Within each channel interval, one to six Bouma Sequences were observed that are separated by very thin intervals of siltstone or mudstone. These sands are characterized by irregularly distributed calcite-cemented zones those are contrasted markedly with the surrounding silica and clay-cemented sandstones. Observed calcite cemented zones are divided based on their shape as blocky, spike-like, and elliptical bodies. The most abundant cemented intervals appear as blocky zones which are 2 to 12 in. thick, whereas spikes have visible terminations in core and are less than 1 in. thick. Elliptical zones have displacive texture and a maximum diameter of 2 in.

Prediction of the distribution of these calcite-cemented, non-reservoir intervals is an important step in reservoir characterization because their distribution influences both the path of fluid flow and reservoir compartmentalization. The calcite-cemented zones appear to be capable of acting as either barriers or baffles to flow within the reservoir. This study documents calcite cement distribution and morphology in the sands in an attempt to predict the lateral extent of these cemented- reservoir intervals by correlating the widely spaced well data in related submarine fan complexes. Evidence of fossils dissolution and the presence of large carbonate rock fragments in the Cherry Canyon suggest that carbonates deposited within the channel sands could be a potential source of calcite cement. The presence of these potential barriers and baffles to fluid flow within highly complex reservoir geometries will impact primary, water-flood, and CO2-flood recoveries.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013