Abstract

In an oil/gas well drilling operation, loss circulation of the drilling fluid in a thief zone is a major problem without a unique solution. This problem is mitigated by using Loss Circulation Materials (LCM). One method to counter this problem could be the use of gel forming polymer systems; that would gel and seal the undesired zones and prevent losses.

In this work interaction of a commercial grade hydrolyzed polyacrylamide (HPAM) and a HPAM derivative with polyethleneimine (PEI) was studied, for the possible use of these polymeric systems as a loss preventive and sealing agent. These studies involved the identification of the optimum polymer/crosslinker concentration followed by their thermal stability testing. Dynamic rheology tests were conducted on the systems in order to examine their pre and post-gelation behavior. Differential Scanning Calorimetry (DSC) was used to study the gelation kinetics of the systems. Selected systems were then tested on a see through flow system to observe their performance in a porous media.

It was observed that attaining an optimum polymer/crosslinker identification is an essential first step towards attaining a rigid and stable gel. At optimum concentrations stable gels were obtained. Gel strengths were greatly enhanced by increasing temperature and aging time. This was reflected in both the rheology and the DSC tests. The DSC experiments provided great insight into the gelation mechanics of the polymeric LCM systems. For the best two systems, 100% solution to gel conversion was attained in nearly three and a half hours of total ageing time at 100°C isothermal condition. The same gelants when tested on the see-through flow setup were able to successfully prevent mud loss in a zone having 36% porosity and 300 D permeability at room temperature and moderately high pressure conditions.

This paper will build on and substantiate the idea of utilizing cross-linked polymer gels as LCM. It will introduce the findings of a self-fabricated see through experimental setup that related the cross-linked polymeric LCM's behavior with differential pressure, in a porous media.

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