Connectivity is a fundamental but oftentimes elusive characteristic that influences injection and production rates, path of the fluid and field economics. Predicting and measuring connectivity is an important activity for reservoir management. Reservoir simulation is a good tool for connectivity evaluation because of its flexibility. That flexibility, however, comes at a price of time and data needed to develop the geological model and obtain a history match. Several powerful alternatives to simulation exist and we present two here.
The methods to estimate connectivity fall into two camps: one that uses flow rates and well pressures in a deterministic model and one that uses geological data with statistical methods. The deterministic method, called the capacitance model (CM), provides a quantitative measure of connectivity for each injector-producer well pair. The results can be used to predict future production and identify geological features which are affecting connectivity. A statistical, percolation-based method (PBM) estimates the probability that a well pair will be connected. The PBM uses sand body sizes and well distances to make its predictions for use in infill drilling campaigns and production estimates.
Using three case studies, we describe how the CM and PBM can be used to give results that do not require simulation. We show how well spacing for an infill drilling campaign can be chosen using PBM to reduce risk in a low-permeability oil reservoir under waterflood. CM is applied to a conventional gasflood and a heavy-oil waterflood reservoir to predict production and validate the field geological models.
Jerry Jensen holds the Schulich Chair in Geostatistics at the University of Calgary’s Dept. of Chemical and Petroleum Engineering and is an adjunct professor in the Geosciences Dept. Prior to joining the U. of Calgary in 2007, Jensen held faculty positions at Texas A&M (2007) and Herriot-Watt (1997) Universities and worked as a field engineer for Services Techniques Schlumberger (1977) and Gearhart Industries (1983).
He is a co-author of 90 publications, including “Statistics for Petroleum Engineers and Geoscientists” published in 2000 by Elsevier. Jensen has served as technical editor for the SPE (1998-2001) and editor-in-chief for Natural Resources Research (2007-2010). He holds a PEng with APEGGA. Jensen received a BSc in electrical engineering from the University of Birmingham, UK, in 1973 and a PhD degree in petroleum engineering from the University of Texas at Austin, Texas, USA, in 1986.