Producer Well Temperature Control and Optimal Oil Production During a Steamflood

Abstract

Abstract Steam injection is an important method for recovery from heavy-oil reservoirs. A major issue for steam flood operations is the high temperature at the producer well after steam breakthrough. Surface facilities need to be equipped with procedures to handle hot fluids exiting the well head. Wells are sometimes shut in for safety or other practical reasons because they are too hot. There are multiple parameters that influence producer temperature. The focus of this paper is to study the impact of injected steam quality and pressure using reservoir simulation. We find that a combination of high-quality and high-pressure steam injection conditions, followed by injection of steam at reduced quality and reduced pressure achieves larger cumulative oil recovery and reduces producer operating temperature thereby avoiding shut-in. Steam injection at reduced quality, and at lower temperature and pressure, prolongs the producing time of the field, thereby increasing the cumulative volumes of oil recovered. Injection of low quality steam, however, increases operating costs with larger water consumption for steam (CWE) and a larger water production for disposal or reuse. On the other hand, the greater the steam quality, the greater the energy required (BTU) for steam generation. To investigate such tradeoffs, we used a commercial simulator to model a hypothetical layered reservoir with a steam injector and two producers. A steam of quality 1 at 800 psi is injected initially, followed by injection of a lower quality and/or lower pressure/temperature steam in order to keep the producer well temperature below 450 °F at all times. Our systematic study of steam pressure or temperature and quality leads to the following observations for the particular reservoir characteristics: (i) Reducing steam pressure and quality led to lower cumulative produced oil volume, with better temperature control at the producer well; (ii) For the same amount of energy injected (in BTU units), higher steam quality produced more oil, but led to elevated temperature at the producers and shutting-in of the wells; and (iii) Steam flood with alternating periods of high- pressure, high-quality injection and periods of lower pressure injection led to continuous oil production with producer temperature control. The hybrid injection schedule consists of a combination of alternating high-quality and high-pressure steam flood, followed by reduced steam quality and reduced pressure. Importantly, larger cumulative oil production with lower cumulative energy and water injection resulted from hybrid injection. We also include geomechanical effects to assess any impact of pressure variations and conclude that the hybrid injection strategy is a promising solution for heat control at producer wells.