Controlled Acid Jet (CAJ) Technique for Effective Single Operation Stimulation of 14,000+ ft Long Reservoir Sections

Abstract

Abstract Horizontal wells with continuous reservoir sections between 10,000 and 20,000 ft are being used for the development of the laterally extensive low permeability chalk in the Dan/Halfdan oil accumulation, offshore Denmark. The concept, design and practical experiences from an efficient and effective completion and stimulation method, Controlled Acid Jet1 (CAJ), which has been developed to stimulate very long horizontal well sections in a single operation, is described. It is a non-cemented liner, with a limited number of unevenly spaced holes (perforations) which ensures efficient acid stimulation of the complete reservoir section, provided the acid is pumped at sufficiently high rates. The CAJ liner has in several ways set new standards for the completion and stimulation of long horizontal wells. The most significant achievement with the CAJ liners is the remarkably effective acid coverage with efficient stimulation of reservoir sections up to 14,400 ft in a single operation. This is more than 20 times the interval length covered during matrix acid stimulation in a traditional cemented and perforated liner. The CAJ liner completion and stimulation concept has proven to be efficient, uncomplicated to install and very cost effective. Currently, 35 CAJ liners are producing from more than 220,000 ft of reservoir sections in the Dan West Flank/Halfdan field. The production performance of the wells completed with the CAJ system is concluded to be superior to the performance of wells completed with conventional systems.