Judy Creek Miscible Flood Introduced Fluids Monitoring
Authors: Wu R.S. , Fish R.M. , Batycky J.P. 
Published: March 2010

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:the collection and analysis of gas and liquid samples from wells exhibiting solvent production;the application of a tuned Peng-Robinson equation-of-state (EOS) to match gas and liquid compositions and gas/oil ratio (GOR); andin those cases where EOS matches were successful, solvent production was quantified and the miscibility state was identified.

Because a wide range of LPG sources, and hence compositions, have been used in flood, the blending of LPG and dry gas into solvent was performed through a microprocessor controlled application of the miscible equivalence (ME) technique(1). Therefore, by providing evidence of first-contact miscibility, the monitoring program also provided a rest 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 provide 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 was employed. One of them, a produced fluid monitoring program, was implemented in November 1985. The basic premise of this program is that the composition of a produced hydrocarbonfluid can be used to determine the nature of the miscible process. Furthermore, the program was also intended to provide a quantitative ssessment of the volume of produced solvent.

The monitoring program consisted of first, produced fluid sampling and compositional analysis, and second, 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. This was found to be considerably superior to obtaining only oil samples, and with time, it was recognized that gas-only sampling was sufficient and preferable. Also with time, it became dear that the data obtained from this monitoring program could be used to fully quantify the volume of solvent in the produced 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. Because the injected solvent has had, over time, a wide range of ethane and propane concentrations and given our previous success in lumping intermediates(2) these components are, for most practical purposes, lumped together as a single component.

Figure 1 shows a pseudoternary diagram based on blending various amounts of Judy Creek BHL ‘A’ Pool reservoir oil and solvent at separator conditions of 45 ºC and 2100 kPa.