Patent EA-004518-B1 (EA)
Title: Evaluation of multilayer reservoirs
Inventor: POE BOBBY
IPC: E21B43/14
Filed: 2001-09-12
Abstract: 1. A method for providing production optimization efficiency of well reservoir completions having a plurality of completed intervals via quantitative analysis procedure for reservoir and fracture properties using commingled reservoir production data and production logging information, comprising the steps of: measuring pressure for defined zones in a reservoir; selecting a pressure traverse model available for computing the bottom hole flowing and static wellbore pressures from surface pressures, temperatures and flow rates, characterized in defined zones for measuring pressure in a reservoir are midzone, computing midzone pressures using the traverse model; comparing the computed midzone pressures with the measured pressures; modeling the bottom hole pressure of the reservoir based on the traverse model. 2. The method of claim 1, characterized in that the comparison step comprises either accepting the computed midzone pressures if the computed midzone pressures are within a predefined tolerance of the measured pressures or rejecting the computed midzone pressures if the computed midzone pressures are outside of the predefined tolerance. 3. The method of claim 2, characterized in that upon rejecting the computed midzone pressures the computing step and the comparing step are repeated until the computed midzone pressures achieve the predefined tolerance. 4. The method of any of the preceding claims, characterized in that the reservoir is separated in to defined intervals from top to bottom, each having a top point, midpoint and a bottom point, and wherein the wellbore pressure traverse is computed using the total reservoir commingled production flow rates to the midpoint of the top completed interval. 5. The method of claim 4, characterized in that the fluid flow rates of the wellbore between the midpoint of the top and a second completed intervals are computed using the total fluid phase flow rates of the commingled reservoir minus the flow rates from the top completed interval. 6. The method of claim 5, wherein the pressure traverse in the wellbore between the midpoints of the second and lower completed intervals is computed using the fluid phase flow rates that are the difference between the commingled reservoir system total fluid phase flow rates and the sum of the phase flow rates from the top, second and lower completed intervals. 7. The method of claim 6, wherein the mathematical relationships that describe the fluid flow phase flow rates of each of the completed intervals for oil, gas, and water production of the j<TH> completed interval are as follows: qoj(t) = qot(t)foj(t), qgft(t) = qgt(t)fgj(t), qwfj(t) = qwt(t)fwj(t), where: qoj is the j<TH> wellbore segment hydrocarbon liquid flow rate, STB/D, qot is the composite system hydrocarbon liquid flow rate, STB/D, foj is the completed interval hydrocarbon liquid flow rate contribution of the total well hydrocarbon liquid flow rate, fraction, qgj is the interval gas flow rate, Mscf/D, j is the index of completed intervals, qgt is the composite system total well gas flow rate, Mscf/D, fgi is the j<TH> completed interval gas flow rate fraction of total well gas flow rate, fraction, qwj is the j<TH> completed interval water flow rate, STB/D qwt is the composite system total well water flow rate, STB/D, fwj is the j<TH> completed interval water flow rate fraction of total well water flow rate fraction. 8. The method of claim 7, wherein the corresponding fluid phase flow rates in each interval of the wellbore are defined mathematically for oil, gas and water for the nth wellbore pressure traverse segment as follows: 9. The method of any of the preceding claims, wherein the flow rate and pressure traverse computation in the computation step are performed in a sequential manner for each interval, starting at the wellhead and proceeding to the deepest completed interval. 10. The method of any of the preceding claims, wherein the measured pressures of step a are obtained from production logs or from pressure gauge recordings. 11. The method of any of the preceding claims, wherein the measured fluid phase flow rates of step a are obtained from spinner measurements or from production logs. 12. The method of any of the preceding claims, wherein the measured pressures of step a are permanent downhole guage measurements. 13. The method of any of the preceding claims, wherein the measured fluid phase flow rates of step a are obtained from permanent downhole flow meter measurements or spinner survey measurements.