Paper: Combining Transient Rate And Pressure Data With Production Logging For Enhanced Well Test Analysis

Many gas wells drilled today are completed over 100 ft or more of gross pay interval to maximize deliverability, reserves, and revenue. Formation permeability of these wells is usually very low (less than 1 md). Use of conventional transient pressure analysis to understand formation properties is seldom done because of time (many days or even weeks) needed to acquire correct answers. Knowledge of producing zones and their respective amounts are rarely studied. Such limited knowledge concerning formation properties (permeability, pressure, drive mechanism, etc.) and flow profiles can often lead to poor reservoir management throughout the life of the field and eventually leave many thousands of dollars of reserves behind. Combining production logging with the transient rate and pressure analysis (TRAP*) allows one to identify the wellbore's flow profile and formation flow properties such as permeability, average reservoir pressure, and skin factor (near wellbore and total skin) in less than one day. Such combination testing can identify flow regime, drive mechanism, coning or fingering problems, unusual pressure or zonal depletion, presence of crossflow, scale, or plugged perforations; all of which if identified in time, can be used positively to maximize production and revenue. The TRAP technique uses the production logging tool. First, up and down passes over the perforated interval are made prior to the well test to identify the well's flow profile. Production logging passes made at varying flow rates can further be used to identify the reservoir flow behavior, and the associated reason. For the well test part, the TRAP technique incorporates measuring changing rate data with the corresponding pressure data during a buildup, drawdown, or multi-rate test. Using the principle of superposition (continual integral 1, it eliminates wellbore storage problems and identifies formation flow properties in a very short time frame. The TRAP technique is illustrated through the analysis of two deep gas well tests.