FORECASTING RESERVOIR THICKNESS WITH FRACTALS

THE NATION DESIRES TO EXPAND THE USE OF CLEAN BURNING, COMPETITIVELY PRICED NATURAL GAS. THE INCREASED DEMAND FOR NATURAL GAS HAS PROMPTED NEW DRILLING IN ESTABLISHED GAS FIELDS. THE PROPER PLACEMENT OF THE NEW WELLS IS DEPENDENT ON THE GAS FORMATION PROPERTIES BETWEEN THE EXISTING WELLS. ONE OF THE PROPERTIES IS THE THICKNESS OF THE GAS BEARING ZONE. IT IS GENERALLY ACCEPTED THAT THE FORMATION THICKNESS BETWEEN WELLS IN NATURAL GAS RESERVOIRS CAN BE SATISFACTORILY ESTIMATED WITH CURRENT TECHNOLOGY. UNFORTUNATELY, CURRENT METHODS OF ESTIMATING THICKNESS SUCH AS ISOPACH MAPS BASED ON EXPERIENCE, JUDGEMENT, AND INTUITION HAVE PROVEN INEFFECTIVE IN PREDICTING THE FORMATION THICKNESS ENCOUNTERED BY INFILL WELLS DRILLED IN A GAS RESERVOIR. THE INFILL WELLS WERE DRILLED IN A ONE TOWNSHIP AREA WHICH ENCOMPASSED 115 PRIOR WELLS. SIX WELLS CUT A CUMULATIVE OF 187 FEET OF GAS PRODUCING FORMATION WHERE 320 FEET WERE ANTICIPATED. THE 200-ACRE WELL SPACING DID NOT PROVIDE THE SMALL SCALE INFORMATION REQUIRED TO ACCURATELY ESTIMATE THE INTERWELL THICKNESS. FRACTAL GEOMETRY IS A NEW MATHEMATICAL TOOL THAT HAS APPLICATION IN SOLVING THE SMALL SCALE DATA PROBLEM. FRACTALS ARE BASED ON THE RECURRING NATURE OF NATURAL SYSTEMS AT VARIOUS SCALES. THE FRACTAL PROPERTIES DETERMINED FROM THE LARGE SCALE, AREAL VARIATION IN THICKNESS MEASURED AT THE EXISTING WELLS WILL BE USED TO PREDICT THE INERWELL (SMALL SCALE) THICKNESS AT THE INFILL DRILL SITES. THE OBJECTIVE OF PHASE I IS TO DEVELOP A PREDICTIVE TOOL, BASED ON FRACTAL GEOMETRY, THAT WILL GENERATE ESTIMATES OF INTERWELL THICKNESS. THE ACTUAL THICKNESS MEASURED AT THE EXISTING WELLS IN THE RESERVOIR WILL BE A CONDITION OF THE FRACTAL ESTIMATES.