Solvent Placement Improvement By Pre-Lnjection Of Water, Lobstock Cardium Unit Pembina Field
Authors: Kloepfer C.V. , Griffith J.D. 
Published: December 2007

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This paper is to be presented at the 39th Annual Fall Meeting of the Society of Petroleum Engineers on Oct. 11–14, 1964, in Houston, Tex., and is considered the property of the Society of Petroleum Engineers. Permission to publish is hereby restricted to an abstract of not more than 300 words, with no illustrations, unless the paper is specifically released to the press by the Editor of JOURNAL OF PETROLEUM TECHNOLOGY or the Executive Secretary. Such abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in JOURNAL OF PETROLEUM TECHNOLOGY or SOCIETY OF PETROLEUM ENGINEERS JOURNAL is granted on request, providing proper credit is given that publication and the original presentation of the paper.

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Stratification of petroleum reservoirs plays an important role in the performance of fluid injection pressure maintenance recovery projects. The significance of this factor in miscible recovery applications is emphasized because of the generally adverse mobility ratios common to this type of project. The initial distribution of a miscible slug among the strata of a reservoir dictates the volume of the reservoir that can be miscibly swept as the slug is subsequently driven through the reservoir. The slug volume required to achieve miscibility in all strata of any given reservoir generally becomes prohibitively large. Improvement in permeability contrast prior to solvent placement will effect improved solvent utilization and enhance the efficiency of this recovery technique.

The reservoir in the Lobstick area of the Pembina Cardium pool is severely stratified. In the area of miscible application a conglomerate member, representing about 30 per cent of the reservoir volume, has a capacity of about 50 times that of the underlying sand. To improve the native capacity distribution and to afford an evaluation tool for early injection performance, a 400,000 bbl slug of water was injected ahead of the solvent slug. Theoretically, this pre-injection of water will double the effectiveness of the injected solvent. The calculation method for determining the improvement of solvent placement for Lobstick is described in detail.

Introduction

In miscible fluid displacement projects, reservoir stratification may significantly affect recovery because of the adverse mobility ratios common to such schemes. Solvent injection into a stratified reservoir will generally result in more permeable strata receiving a solvent volume in excess of that required to effect complete miscible displacement, before the less permeable zones have received the required minimum. The initial distribution of solvent among the reservoir strata governs the portion of the reservoir that can be miscibly swept by the driving of this slug through the reservoir. By improving the permeability contrast of the strata prior to solvent injection, the over-all recovery efficiency of a miscible project can be improved.

In the Lobstick Unit, the stratification of the Cardium reservoir is severe and calculated solvent placement inefficient. Theoretical considerations indicate that solvent placement will be improved through injection of a water bank ahead of the solvent. Consequently, 400,000 bbl of water were injected prior to commencement of solvent injection. The calculated improvement in solvent distribution is the subject of this paper.