A monitoring method using distributed temperature sensing (DTS) with fiber optics has recently been used to assess downhole conditions in heavy oil environments, and its capabilities have enabled better reservoir management and improved production. With this method, an optical fiber to monitor temperature real time over the entire length of a well is installed. Custom visualization and analysis software then uses the DTS data to perform analysis of well conditions. The analyses facilitate improved heat management in heavy oil wells by detecting problem areas within the well through comparison of a large number of data sets.
The fiber-optic technology was initially deployed in a steamflood well in Bakersfield, California over ten years ago. Since that time, the technology has been applied in many different producing environments and has proven that monitoring of downhole conditions can provide valuable information for production assessment.
This paper will discuss the significant benefits gained from using this technology in heavy-oil monitoring scenarios. Whereas traditional methods are limited to measuring steadystate conditions or single-point dynamic conditions, DTS surveys can provide real-time temperature profiles over the entire length of the well. Then, by manipulating the wellbore temperature, the dynamic temperature information that is obtained as a result of the manipulation quickly identifies changes in wellbore conditions that can impact production scenarios.
The capability to instantly view the temperature distribution along the length of a well allows use of analytical methods not previously available with traditional survey methods for heavy-oil producing fields. In typical scenarios, this type of field generally employs some form of thermal-enhanced oilrecovery technique. In many cases, a field consists of producing, injection, and observation wells, and by properly balancing the operation of each type of well, recovery costs can be minimized as well as production maximized.
Several factors of an injection system affect field economics. The steam-injection rate is one of the critical factors; therefore, properly setting the injection rate is an important step for efficient field operation. If the steam injection rate is set too low, overall lower production, loss of the steam chest, and possible loss of reserves can result. If the injection rate is set too high, excessive fuel costs, wasted heat in the casing, sanding problems in producers, premature equipment failures, and decreased reliability of well and surface systems can occur.1,2,3
Excessive injection rates can result in early steam breakthrough in the formations and even surface eruptions.4,5
Early detection and correction of abnormal or improper injection conditions in these wells can improve the economics of the field by enabling the optimization of injection rates.
A technology that would provide continuous systematic temperature analysis of the field would be the ultimate method to optimize injection and recovery operations. However, the cost of such surveillance would be prohibitive. Because of the elevated field temperatures, permanent gauges have proven to be unreliable. Traditionally, wireline logging has been used to provide a solution for temperature analysis difficulties.