A Systematic Approach to Identifying Hydrocarbon Sweet Spots Using Integrated Seismic Multiattribute, Wireline-Log, and Core Analyses

An investigation of the Campanian Taylor sandstone conducted using three-dimensional seismic, core, and wireline-log data in the Serbin field straddling Lee, Fay- ette, and Bastrop Counties, southeast Texas, documented storm-dominated shelf sandstone reservoir deposits. By integrating seismic multiattribute analysis, neural net- work techniques, and core data, we were able to predict the distribution of hydrocarbon sweet spots and generate 90°-phase amplitude-for-lithology maps to demonstrate that the Serbin field is separated into two areas: (1) a diagenetically altered, high-frequency, high-gamma- ray, and high-acoustic-impedance area in the western section, suggesting low-porosity rock, and (2) a low- frequency, low-gamma-ray, and low-acoustic-impedance area located in the eastern section, suggesting that the eastern part is composed of relatively high porosity sandstones. The results also demonstrate that although individual sandstone beds are lenticular and discon- tinuous, they collectively constitute a linear geometry, trending northeast to southwest. A neural network proce- dure that relates gamma-ray-log data to a corresponding

instantaneous frequency, resistivity, and integrated seis- mic trace shows that the eastern section of the field can be divided into three zones: zone 1, composed of approx- imately 2–8-ft-thick (~0.7–2.7 m) sandstone-rich zones of moderate frequency (25–30 Hz); zone 2, composed of high-frequency (33–60 Hz), diagenetically altered, mudstone-rich zones; and zone 3, composed of approx- imately 5–13-ft-thick (~1.7–4 m) sandstone-rich zones of low frequency (0–18 Hz) and relatively high porosity. In addition, we demonstrate two additional findings: (1) Hydrocarbon sweet spots are laterally separated by mudstones and calcite- and quartz-cemented sand- stones and are identified by a combination of resistivity and seismic quality factor (Q) attribute sections; and (2) within the Taylor sandstones in Serbin field, poros- ity increases with depth. Finally, although the methods adopted in this research can be applied in other fields with similar geology and limited well control, the appli- cation of the 90°-phase-rotated amplitude-for-lithology method is limited by the low acoustic impedance of the rock under investigation.