Abstract

A produced fluid monitoring program for the Judy Creek BHL 'A' Pool hydrocarbon miscible flood was implemented as a basis for quantifying solvent production and for monitoring miscibility. The program involved: 1) the collection and analysis of gas and liquid samples from wells exhibiting solvent production, 2) the application of a tuned Peng-Robinson equation of state (PRE OS) to match gas and fluid compositions and gas/oil ratio (GOR), and 3) in those cases where PREOS matches were successful, solvent production was quantified and the miscibility mechanism was identified.

Since a wide range of LPG sources, and hence composition, has been used in the flood, the blending of LPG and dry gas into solvent was performed through a microprocessor controlled application of the miscible equivalence (M EJ technique (1). Therefore, by providing evidence of first contact miscibility, the monitoringprogram also provided a test of the automated ME technique. The produced fluid monitoring program, over the course of three years, has revealed that the ME technique has been successful, and that gas analysis data provides the best basis for the determination of solvent production volumes and flood miscibility.

Introduction

In May of 1985, a hydrocarbon miscible flood was initiated in the Judy Creek BHL 'A' Pool. This flood was designed to be first contact miscible (FCM), and to ensure this condition, a variety of safeguards were employed. On of them, a produced fluid, monitoring program was implemented in November of 1965. The basic premise of this program is that the composition of a produce hydrocarbon fluid can be used to determine the nature of the miscible process. Furthermore, the program was also intended to provide a quantitative assessment of the volume of produced solvent.

The monitoring program consists of firstly, produced fluid sampling and compositional analysis, and secondly compositional modelling to match the analysis results. The produced fluid sampling portion of the program originally consisted of obtaining one separator oil sample from a well in each of the miscible flood patterns every three months After one round of sampling and modelling it became apparent that oil samples alone did not provide sufficiently accurate information for modelling purposes. Hence, in the second and subsequent rounds, both gas and oil samples were obtained. Thus was found to be considerably superior to obtaining only oil samples and with time, it was recognize that gas only sampling was clearly sufficient and preferable. Also with time, it became clear that the data obtained from this monitoring program could be used be fully quantify the volume of solvent in a produce hydrocarbon stream.

Monitoring Program Theory

To illustrate the concept behind the fluid monitoring program, Judy Creek BHL 'A' Pool reservoir fluid and solvent compositions are used. These are shown in Table 1. Since the injected solvent has had, over time, a wide range of ethane and propane concentrations, these components are, far most practical purposes, lumped together as a single component.

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