The Benefits of Reinjecting Instead of Flaring Produced Gas in Unconventional Oil Reservoirs

Abstract

Over the last decade, there has been tremendous success is developing and producing unconventional oil resources such as the Bakken and Eagle Ford; however, flaring produced gases from these fields has become a problem that needs to be addressed. In many instances, pipeline infrastructure is not in place to transport gas away from the wells. One possible solution is to reinject the produced gas back into the formation, which has numerous positive benefits. It has the potential to increase oil recovery from unconventional reservoirs because of the strong likelihood to achieve miscibility with reservoir oil. Furthermore, unlike flaring, the injected gas will be available for sales once gas gathering pipelines become available. Gas reinjection also should mitigate environmental concerns associated with greenhouse gas emissions. We evaluated the recovery potential along with the costs of reinjecting gas to determine the economic value of this process. A dual-porosity, compositional flow simulator was used to model the gas injection process into a well surrounded by producers and to determine the amount of incremental oil and gas produced. We calculated the net economic value of the process by including the cost of gas compression and fuel gas for injection. We have concluded that oil production rates can be significantly increased, and the economics of the process is very positive. Additionally, significant volumes of gas can be recycled, which alleviates environmental concerns of gas flaring and improves resource efficiency. As a result, we recommend pilot testing the gas injection process to assess the commercial application of the proposal. Introduction Flaring natural gas has become a major issue in unconventional liquid-rich reservoir development. This problem is particularly bad in the Bakken where close to 40% (Helms, 2014) of the produced gas is being burned, but it is also a problem in the Eagle Ford area where over 50 billion standard cubic feet (Bcf) was flared last year. It has become a visible national issue with many reports from the national media and major newspapers (Krauss, 2011), congressional hearings (Upton, 2014), and governors starting task forces to address it (NDPC, 2014). A popular way to display the problem is to show “Earth at Night” images from before and after the unconventional revolution. Figure 1 has two of these images of the U.S., one from 2003 and one from 2012. From these two images, both the Bakken area and the Eagle Ford can be clearly observed to have an increase in “lights”. While some of this may be attributed to actual lights from drilling and workover rigs, the majority of this light comes from burning natural gas in flares. URTeC 2014 Page 1640