Abstract

Differential initial production was recorded between four on-structure, single-pad horizontal wells targeting the Eagle Ford shale in South Texas, USA. Drill cuttings from two up-dip and two down-dip laterals were captured on the next adjacent pad and analyzed using Energy Dispersive X-ray fluorescence (ED-XRF), powdered X-ray diffraction (PXRD), and programmed pyrolysis analyses prior to completion. Results were used to evaluate reservoir quality before investigating completions strategy as the two major factors responsible for overall production.

Although mineralogy and elemental signatures related to organic richness and paleodepositional environment were similar between the up- and down-dip laterals, a few key organic geochemical parameters differed along the dip. Although a subtle difference in thermal maturity assessed through pyrolytic Tmax values was noticed between up- and down-dip laterals, Hydrogen Index (HI) values and calculated Transformation Ratios remain very consistent among the wells. Additionally, estimated oil cracking does not yield significant differences among the laterals.

In this case, estimated secondary gas cracking does indicate that up to 65% increase in secondary gas generation may have resulted in creating greater gas-drive potential and produced greater oil recovery. Gas-drive is known as an important factor in Eagle Ford production and this differential in secondary cracked gas may be principally responsible for the greater oil production post completion. Measuring the gas/oil ratios in the up- and down-dip laterals during initial flow-back testing over a period of sustained production is now underway and may demonstrate this inferred difference in secondary gas generation between up=and down-dip laterals.