Sand production has remained a challenge within the oil industry for many years. Gravel pack completions has been the primary method for addressing sand control in countries like Ecuador where reservoirs with high-permeability unconsolidated formations exist, such as in the Oriental basin. Although gravel packing has been a good solution for addressing sand production, challenges related to well geometry, short net pay, and even cases of corrosion and material failure still exist.
For these reasons, research has focused on new techniques to prevent sand production. Chemical sand consolidation can provide additional strength to maximize the sand-free fluid rates. This paper discusses a proposed chemical treatment to consolidate a near-wellbore (NWB) area to remediate a gravel pack completion that had become damaged in Well F21, which produces 22° API oil from the M1 sandstone in T Block, Ecuador, South America.
Well F21 was completed using gravel packing in June 1999; but, after more than 10 years, gravel and formation sand became present in the flow stream, causing the electrical submersible pump (ESP) to experience sticking problems, making it almost impossible to produce oil from the well.
Chemical sand consolidation using a premixed two-resin component system was tested in the laboratory using the sand formation and gravel samples from the selected well. The laboratory results showed that it was a good alternative to consolidate not only the formation sand, but also the gravel still present in the current completion. In October 2011, the well was intervened, pumping the sand consolidation material using coiled tubing (CT). After treatment, the well was placed back on production with the ESP and initial production was 600 BOPD with no sand.
This paper presents a case history of chemical placement and gravel pack completion repair in the Oriental basin. After the treatment, the formation was completely consolidated in the NWB area, with no sand production after well production was reinitiated. The results lead to additional well applications in Ecuador, providing new opportunities to effectively produce unconsolidated sand reservoirs in this basin.
Unconsolidated formations can exhibit typical characteristics that can be evaluated using sonic surveys and rock mechanics laboratory analysis. An extreme unconsolidated formation has a total absence of cement in its pore spaces to create good compressive force; therefore, taking a rock sample for laboratory evaluation can become a difficult task. This particular phase requires novel procedures for evaluation of rock mechanics modules in downhole conditions. Theories, such as Mohr-Coulomb, should be applied to a step rate test. Typically, the sonic survey can provide good evaluation; but, in cases of poor cement bond logs, limitations can arise.
A better knowledge of lithology can lead to job optimization to minimize future production loss. Typically, a reservoir with good permeability (more than 350 md) could be good a candidate for sand consolidation. A bigger net pay (more than 60 ft) can present limitations. In cases of gravel pack repair, procedures can be optimized if only a short portion must be fixed. It is necessary to run an image logging tool to evaluate the top and base of the gravel pack. In cases of limited size, other tools can be used to view damaged portions, such as a downhole video camera.
In the case history discussed, it was not necessary to run logging tools because of the short gravel pack size and the entire production interval was consolidated.
