Abstract

The effect of PVT data quality on simulator estimation of liquid hydrocarbon recoveries under various gas sales scenarios was investigated. An extended black oil reservoir simulation model together with the fluid model from the Third SPE Comparative Solution Project and a gas condensate fluid from Drohm Project and a gas condensate fluid from Drohm et al were used.

Experimental constant volume depletion (CVD)) liquid saturations were modified by the method of Drohm et al. The unmodified and modified gas condensate data sets were used to generate equation of state (EOS) characterisations and black oil PVT tables for input to reservoir simulation.

The EOS characterisations were constrained to reproduce the liquid saturations. For the modified data it was possible to match both the observed dew point and the modified liquid saturations. However, the EOS characterisation which was matched to the raw liquid saturations underpredicted the experimentally measured dewpoint.

The applicability of the black oil simulation model is discussed and various scenarios are compared to show the influence of data corrections on simulation results.

Introduction

Estimated hydrocarbon recoveries are subject to various sources of uncertainty, the impact of which is dependent upon the class of reservoir fluid. Each of these uncertainties must be investigated individually to assess their collective impact. The impact of uncertainties in phase behaviour on estimated liquid recoveries phase behaviour on estimated liquid recoveries for gas condensate reservoir fluids is considered.

A decision to consider uncertainty must take into account not only the benefit and use of the estimate but also the cost of ignoring the uncertainty. A poor decision can sometimes result as much from a poor evaluation of uncertainty as it can from a poor evaluation of the data. To ensure robust decisions, the uncertainties associated with input data should also be evaluated.

Estimated hydrocarbon recoveries under various production scenarios determine whether a hydrocarbon reservoir can be economically exploited. Each class of hydrocarbon deposit has specific associated uncertainties/problems that impact on these estimated recoveries. This paper builds on the work of Drohm et al, where paper builds on the work of Drohm et al, where corrections are made to gas condensate PVT data, hence only gas condensate reservoirs are considered here.

"The importance of gas-condensate reservoirs has grown continuously since the late 1930's."

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