A Shrinkage Factor Model Application to Have a Proper Oil Well Testing Measurement and Allocation Driven from a PVT Equation of State (EOS) Model

Abstract

Pertamina Hulu Energi - West Madura Offshore (PHE WMO) is one of PHE subsidiary which has been operating the West Madura PSC block since May 2011 after Kodeco contract period had ended on the same following date. The block has been actively producing its oil and gas from both major fields located on the northern part (5 production Platform) and the southern part (3 production platform). Both area had contributed to PHE WMO's production peak of 26,281 bopd and 126.4 mmcfd on 2013. The total production came from each well have been accounted either by an installed separator testing equipment or a Multiphase Flow Meter (MPFM). The data test measurement accounted from the installed equipment has to be accurate since the data will not only be used for monitoring yet it will be use within the whole integrated production analysis from subsurface to surface production optimization and studies.

For having a proper reliable testing measurement, a standard condition production rate (60°F and 0 psig) needed to be included within the calculation as per API MPSM Ch.20.1 stating that the measurement should include a SF variable to convert the testing to a stock tank condition. Unfortunately, the installed separator at each field does not yet have the reliable SF and its presence would be critical for the calculation. The study of the shrinkage factor was initially started due to the high difference of cumulative well testing accounted on each platform compared to the final measured oil each day at the gathering station. The problem initially occurs for the southern field that shows only 55% from its tested production at the field were accounted at the gathering station. This became critical since the excluded SF factor form the calculation may result with unreliable production performance and miss calculating the allocation production from the gathering station back to each production well platform.

This paper will mainly discuss the method and workflow for determining the Shrinkage factor model and its application to each field production platforms. The SF model were based on the compositional Model of every PVT lab data for each field using an internal PVT software module and its application has been deliberated within the excel spreadsheet for production operator in the field and it became easy to use. The result itself have successfully met the objective as a reliable SF model once compared to the Shrinkage value estimated by a manual shrinkage tester on the field and the usage has successfully changed the allocation factor for southern field from 55% up to 88 - 95% resulting a reliable production data for every field at West Madura Offshore. Besides achieving the correct measurement, the PVT model had affect other integrated studies such as reservoir studies, flow assurance studies and even economic valuation studies which actually made a big impact to the company.