Insitu Heat Generation for Near Wellbore Asphaltene and Wax Remediation

Abstract

Abstract Organic deposits such as paraffin and asphaltene in the near-wellbore region are common damage mechanisms in oil wells, especially in brown fields, and account for major production losses from these fields. Typical efforts to mitigate these problems include pumping of several types of remedial treatments to inhibit or dissolve deposits, pump heated fluids as in hot oil treatments, or use mechanical methods such as cleanouts with jointed pipes and coiled tubing. Most of these methods are not time and cost-efficient for two reasons. First, such treatments are usually not one-time solutions but are required at periodic intervals depending on the severity of the problem. Second, the specific requirements such as long soaking time, exotic chemical systems, large equipment footprints, safety etc., often add to the associated service costs. In some of the fields being developed in the western onshore fields of India, heavy organic deposition across screens and in the near-wellbore region is being experienced. This is suspected to be occurring due to wax appearance temperature being close to the reservoir temperature. The wax dissolution temperature is well above the reservoir temperature, due to which any effective remedial treatment necessitates higher temperature generation for dissolution/inhibition of wax problems. Different types of solvents have been used for remediation purposes and have yielded mixed result. The concept of heat generation by exothermic chemical reactions has also been applied in the field after taking a cue from oil industry application, pipeline pigging industry to tackle the similar problems. On lines of this concept, the authors designed an effective and cost-efficient in-situ heat generation treatment to be applied in oil wells for removal of organic deposits. After laboratory testing using a range of products, the regulated components from the pipeline systems were replaced with safer, non-regulated products to suit oil well treatment. A successful field trial was achieved with the chemicals in generating heat to attain temperatures beyond the wax dissolution temperature, resulting in increased production. This paper documents the steps in developing this system and using it in the field, and aims to describe the challenges encountered, lessons learnt and recommendations for future application of the system. Introduction Bhagyam field is located in western part of India. Numerous exploration and appraisal wells have been drilled in RJ-ON-90/1 block in Rajasthan North West India, primarily targeting the exceptional Fathehgarh reservoir. Many of these wells have encountered hydrocarbon bearing potential reservoir quality rock in the shallower Bhagyam formation. Figure 1 shows the field location, which is located in Rajasthan state, India. Bhagyam formation is a Shallow (300–500 m TVDSS) in general has been described as sandstone with high net to gross, high porosity about 25–30 %, permeability about 1000 md. The Bhagyam tilted fault block structure (Figure 2) is formed at the intersections of NNE-SSW and WSW-ENE faults, it contains Sand layer FB1 to FB-3. The Bhagyam Crude Oil is around 28 API having about 20 cp viscosity at reservoir condition. The source rock in lacustrine in origin, it has generated waxy oil.