A Quantitative Approach for Firewater System Design Optimization in a Marginal Onshore Well Oil Field

Abstract Firewater system is a critical safety system in an oil and gas field. It protects personnel and facilities from fire hazards, especially the effect of jet fire and pool fire on impairment of escape routes and adjacent equipment that could lead to escalation events. It typically comprises of fire pump, fire pond, firewater ring, deluge system, fire monitor, hose reel, etc. However, a complete firewater system might not be cost-effective for a marginal oil field, primarily, an onshore field where the plant area is spacious for escape and escalation prevention. This paper presents a quantitative approach to optimizing firewater systems design in a marginal onshore well oil field. The quantitative approach begins with the identification of fire hazard scenarios. Subsequently, consequence and frequency analyses are conducted for the respective scenarios. A consequence analysis is employed to ascertain whether the scenario could result in escape impairment or escalation. Scenarios that produce neither escape impairment nor escalation are classified as survivable, while the opposites are un-survivable. A frequency analysis is then employed to estimate the likelihood of the aforementioned scenarios, thus enabling the portion of survivable events to be quantified. Mitigation shall be explored for un-survivable events to enhance the survivability portion. Approximately 750 scenarios are identified, resulting in an estimated frequency of 3.62x10-4/year of pool fire events and 6.25x10-5/year of jet fire events. The survivability against fire events is 72%, whilst the un-survivable is 28%. The contributors of un-survivability are escape impairment due to pool fire (25.8%), escalation due to jet fire (1.3%), escalation due to pool fire (1.2%), and escape impairment due to jet fire (0.1%). Furthermore, this study revealed that the majority of escalation events were caused by thermal radiation exposure at 37.5 kW/m2 within 60 minutes. Several mitigation measures have been identified to improve the survivability. All of the selected mitigations rely on manually operated systems, as the critical duration to complete action, 60 minutes based on escalation criteria, can still be satisfied by a manual system. Fire blankets have been selected to mitigate escape impairment by protecting personnel against pool fire radiation during escape. Fire hose reels have been chosen to minimize the escalation due to jet fire by reducing thermal radiation to adjacent equipment. Furthermore, a manual foam monitor is employed to extinguish the pool fire. The implementation of these mitigations has been demonstrated to enhance survivability from 72% to 99% while simultaneously reducing the firewater rate in the absence of automatic firewater users. The methodology has been proven to augment survivability against fire hazards. It can furnish management with a rationale for decision-making. It can be implemented in typical marginal onshore oil fields.