Use of Micro-Resistivity Imaging Tools in Developing Lower Pennsylvanian Morrow Channel Sandstone Reservoirs, Cheyenne, Kiowa and Lincoln Counties, Colorado

Mark P. Germinario

In southeastern Colorado, Lower Pennsylvanian Morrow channel sandstones are part of complex valley-fill sequences incised into Morrow marine deposits. Morrow valleys are approximately 1/2 to 1 mile wide. Valley-fill consists of floodplain and channel filling shales, very fine-grained estuarine sandstones and fine- to coarse-grained channel sandstones that are up to 50^prime thick. Channel sandstones represent a sequence of stacked fluvial bars deposited in braided, anastomosing and meandering fluvial environments. Cross-stratification in channel sandstones can be imaged by micro-resistivity wireline logging tools and interpreted interactively on various workstation software packages. Recognition, interpretation and measurement of current, stoss face, and lateral accretion beds in these sandstones can result in an estimated direction of paleocurrent flow of the channel. Determination of the channel's local paleoflow direction can provide significant sand risk reduction in developmental drilling, especially in 80 acre or less spacing patterns. As the distance between offset drilling locations increases, the reliability of paleoflow prediction decreases, and the corresponding sand risk rises. Lateral accretion bedding in Morrow channel sandstones has proven to be a poor indicator of sand thickening direction, due to the complex stacking of multiple channel sandstones within any given valley-fill sequence. Micro-resistivity imaging reduces risk in Morrow channel sandstone development drilling programs. Furthermore, these interpretation techniques could be app icable in other fluvial channel sandstone plays.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California