Analysis of Production Characteristics and Bottom Hole Pressure Buildup Data – Napoleon Field, Jackson County, Michigan
The Napoleon Field in Jackson County, Michigan represents a significant discovery of oil and gas in the state of Michigan. This reservoir is a fractured and dolomitized carbonate within the Trenton and Black River Limestones.
Early flow from the wells is dominated by flow through the high permeability fractures and vugs, followed by a transitional period in which the lower permeability matrix begins to contribute. Ultimately, the flow becomes pseudosteady-state with most of the contribution from the matrix. The production decline curves that result from this type of production show early excess deliverability that is limited by State production allowables, followed by a transition toward matrix flow. The ultimate decline curve is hyperbolic in nature and largely represents the depletion of the matrix.
Bottom hole buildups run early in the development of the field typically show a humping effect, which is due to the influence of the dual permeability system. Analysis techniques were used to estimate the storativity ratio, ω, as well as conventional estimates of permeability and skin factor. The analysis allowed for estimation of the fracture porosity, especially insofar as it relates to the matrix porosity, which is important in understanding the reservoir. It was determined that about 20% of the hydrocarbons are stored in the fractures/vugs and 80% are stored in the matrix.
The bottom hole pressure tests also revealed what happens when horizontal wellbores traverse multiple reservoir compartments. An example of one portion of the field where this occurs has been shown.
AAPG Search and Discovery Article #90154©2012 AAPG Eastern Section Meeting, Cleveland, Ohio, 22-26 September 2012