Successful Prediction Of Well Productivity From Openhole Logs Improves Profitability In Several Rocky Mountain Formations: Case Histories

This paper describes methods used to quantify reservoir properties through the analysis of openhole logs and integrate the results into completion and stimulation designs. The results show that accurate prediction of well productivity can be made such that stimulation treatments can be designed to truly optimize production from a well. Optimization of stimulation treatment design is greatly dependent on understanding the permeability of the formation. Direct measurement of permeability is not economically available in many "tight" formations. We will demonstrate through integrating log analysis with production evaluation that correlations can be constructed which allow the analyst to interpret in-situ formation permeability from conventional openhole logs. The three formations being presented are: the Mesaverde group of the Piceance Basin, the Frontier formation of the Moxa Arch and the Green River formation in the Uinta Basin. The first two of these formations are "tight" gas sands, and the third is a low-permeability oil-producing formation. In each case the authors have been successful in increasing profitability of the well completions. The Piceance Basin case involves development of a reservoir containing multiple sand lenses. The methods will demonstrate how to accurately predict the gas to be produced from each sand, and therefore improve the efficiency of a completion by selecting only the sands that will contribute significant quantities of gas to pay for the expense of completion. The Moxa Arch case involves development of a single sand. The variation in reservoir quality between wells suggests that variations in stimulation treatment design could improve economics of the development. This paper presents the method used to quantify the individual well quality and design the optimum treatment for that unique well. The Uinta Basin case extends the concepts developed in the two "tight" gas sand plays to oil-producing sands. The results from this development project indicate that production has more than doubled through improved treatment design, which comes from increased reservoir understanding through log analysis. We feel that the presentation of the various methods used in this paper will demonstrate the value of inter-discipline communication concerning the economics of oil & gas exploration and development.