Abstract: Biomarker Methods for Allocating Oil Production to Specific Depth Intervals in Shallow, Low Permeability Reservoirs

Mark A. McCaffrey, Paul A. Lipton, Henry A Legarre

Heavy-oil-containing, low-permeability reservoirs may be suitable for various types of enhanced oil recovery (EOR), such as hydrofracturing, water flooding, and/or steam flooding. Frequently, the ability to attribute EOR-induced production to specific portions of a reservoir could favorably impact the choice of well-completion strategies (such as fracture interval spacing) anchor values for EOR parameters (such as injection rates or the spacing of steam cycling intervals). In low-permeability, shallow reservoirs, biomarker oil biodegradation parameters may offer this ability to the production to specific portions of an oil accumulation, because oil biodegradation can vary both laterally and vertically in low-permeability reservoirs.

Because biodegradation-sensitive biomarker parameters are measured by gas chromatography-mass spectrometry (GC-MS), they enable the investigator to quantify differences in biodegradation while essentially looking "through" the unresolved complex mixture (UCM or "hump") typical of the gas chromatography-FID traces of moderately to heavily biodegraded oils. Our presentation will discuss the three dimensional variation of specific biomarker biodegradation parameters (such as the C₂₅ highly-branched alkane/phytane ratio) in oils from certain California diatomites, and we will discuss potential reservoir management applications of these natural tracer data.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994