Enhancing Design-by-Analogy Procedure of Injection-Well Gel Treatment Sizes by an Integrated Survey of Case Histories

Abstract

Abstract The drive to mitigat water production continues to increase the interest in applying conformance-control gel treatments in mature oil fields. Practically, designs of new gel treatments are adopted from previous case histories conducted in analogous reservoirs. This design-by-analogy procedure requires reservoir engineers to have a thorough knowledge about how gel treatments should be designed and have been mostly applied for each reservoir type. This paper presents comprehensive design guidelines for sizes of injection-well gel treatments based on an integrated survey of worldwide field projects. It also provides the typical and most-applied treatment volumes per reservoir type to be used as a starting point in planning of new jobs. The survey includes 61 gel projects compiled from SPE papers and conducted in 11 different countries between 1985 and 2014. Summaries and distributions of five gel-volume parameters were evaluated using the univariate descriptive analysis and stacked histograms. Scatterplots were used to determine effects of the formation temperature and the treatment timing on treatment volumes. The unsuccessful pilots were compared with productive gel projects to indicate the causes of pilots’ failure. The survey showed that the typical treatment size is 10,700 barrels, 310 barrel per perforated foot, or 19% of the moveable-pore-volume (MPV) of problem zones. Overall, gel volumes are greatly affected by the formation type and larger treatment volumes are placed in sandstones than carbonates and in matrix-rock than other formation types. Frequently, matrix-rock formations are treated with gel volumes >100 bbl/ft while treatment sizes <100 bbl/ft are used to treat naturally-fractured and unconsolidated formations. Gel volumes <3000 or even <1000 barrels are used to treat pipe-like channels in unconsolidated sandstones, treat matrix-rock formations without crossflow, or in economically-designed gel treatments. We have found that increasing the gel volume improves all treatment performances, not just the oil production response, and for all formation types, not just for the matrix-rock reservoirs. Hence, the ‘bigger is better’ rule of the gel volume is also recommended for fractured and unconsolidated formations as for the matrix-rock reservoirs. Instead of searching the literature for few analogs, the new survey provides conformance specialists with a complete overview of gel treatment sizes for all reservoir types. This would markedly facilitate designing of gel treatments and save time needed to identify the analogs for a given candidate reservoir.