Wax Management: Comprehensive Approach to Assure Flow in Harsh Climate-Brown Field Conditions

Abstract

Abstract Wax deposition contributes significantly and painfully to the deliverability of produced fluid along its journey from porous media through the wellbore to the production facilities. Solutions for wax fighting include, but not limited to, chemical, mechanical and/or thermal or a combination. Wax management has been always a key concern for Dragon Oil offshore Turkmenistan as per wax depositions in the wellbore of most producers has driven Dragon Oil to adopt different approaches to handle this critical issue. However, optimizing these approaches is of a paramount importance especially in today's industry situation and also to honor weather changes and logistical challenges while working on controlling wax related issues. Wide range of wax management strategies are practiced to prevent, mitigate and remediate wax deposition. Several studies have been conducted to investigate problem roots and to develop the most practical solution for wax management starting from downhole to the onshore facilities. Chemical injection and mechanical Slick Line (SLK) well interventions are the techniques most commonly practiced in Dragon Oil to manage the deposited wax in the wellbore (~ 100 jobs of wax cut/week and ~ 700 liters/day of wax inhibitor-optimized dosage). Compliance Sheets were designed and being optimized on daily basis to manage such intensive well intervention. Modifications to drilling Basis of Design (BoD) allowing chemicals injection at different depths/dosages and wellhead area thermal treatment are examples of precautions that being followed to secure wax free flow. Wells that are completed in "A-Sand" reservoir have severe wax challenges due to high wax appearance temperature (WAT). Having BHFP < BPP and WHT < WAT makes wax precipitation and deposition an imminent phenomenon. In addition, several studies showed that the above combination along with fluid properties and potentially low velocity contribute to more wax deposition in the tubing. Furthermore, harsh weather adds more challenges to the Company's efforts to manage flow assurance related issues. For example, delays in Slick Line operations due to difficulties in mobilizing SLK units allow more soft wax to build up and become harder at different depths. As a result, significant disturbance in the wells productivity and flowlines deliverability is observed causing losses in the field total production. Plugging of chemical injection systems (control lines and nipple), as first guard in some wells, adds another complication to deal with de-waxing management in the field. Dragon Oil has also successfully applied a few surface thermal means to manage wax deposition in surface facilities that will be discussed also in this study highlighting monitoring, surveillance and optimization efforts. It was observed that optimizing Wax Inhibitor (WI) dosage help in decreasing the frequency of mechanical de-waxing operations. Obviously higher WI dosage rate increases the operational costs and potential side effects (i.e., emulsion, foaming, etc.). Dragon Oil developed a practical approach to thoroughly monitor all wellhead related parameters and managed to add value through the comprehensive optimization cost/effect versus costs/risks of wax management by mechanical, chemical and thermal means.