Huff-N-Puff Gas Injection Pilot Projects in the Eagle Ford

Abstract

The Eagle Ford formation has been an overwhelming success producing around 2 billion barrels of oil over the last seven years, yet its potential may be even greater. The projected recovery factor is only 5-10%, and using improved oil recovery (IOR) methods to increase recovery could result in billions of additional barrels of production. Significant research is required to access this oil, and while a number of companies have field tested an IOR method called huff-n-puff gas injection, most of the published results are from lab and modeling studies. This paper evaluates the results from these field tests and discusses the successes and opportunities. The huff-n-puff process involves injecting a miscible gas into a well, and then after some amount of time, producing back from that same well. The first part of this paper evaluates the publically available data from the Texas Railroad Commission and other sources for these pilots. Analytical techniques are used to predict the amount of additional recovery and the pattern efficiency from this data. This is compared to pre-injection forecasts. All cases show increased production rates with injection, and in one pattern where the data was easiest to interpret, the incremental production has doubled since the huff-n-puff project started. This paper also proposes methodologies for implementing second generation pilots for unconventional reservoirs. It is important to define clear objectives that characterize the value of the pilots. The significance of developing optimum drilling and completion strategies for primary and IOR success is also highlighted. Long term information collecting strategies are proposed along with methods to optimize the projects during the pilot, and contingency plans to deal with difficulties that may arise. Finally, we discuss how the location and infrastructure needs of a pilot are paramount to its success. Using IOR to increase recovery from unconventional oil fields is important for the continued success of plays like the Eagle Ford. Pilot tests are an integral part of developing the best IOR techniques, and this paper provides a thorough analysis of implementing IOR pilots in the Eagle Ford. It also shows how and where it has been applied successfully and discusses ideas to further improve the likelihood of success in the future.

Simulation of High Water-Cut in Tight Oil Reservoirs during Cyclic Gas Injection

“…The recovery factor for huff-n-puff case was 11.46%, which was 1.48 times the 7.74% RF of depletion. The improvement factor of 1.48 matched the field observations in the literature (Wang et al 2017;Hoffman 2018). Table 4.3 shows the component RF of C3.…”

Recovery Mechanisms for Cyclic (Huff-n-Puff) Gas Injection in Unconventional Reservoirs: A Quantitative Evaluation Using Numerical Simulation

“…The final history-match is shown in (Figure 7) and it is very close to the field data Figure 7. Model results (solid dark green line) history-matched to Eagle Ford huff-n-puff gas injection field pilot data from Hoffman [16] shown with light green line and symbols.…”

“…Early in the life of the well, when it is flowing under natural energy, the BHP may be higher than 500 psi, which could be why the model Figure 7. Model results (solid dark green line) history-matched to Eagle Ford huff-n-puff gas injection field pilot data from Hoffman [16] shown with light green line and symbols.…”

“…There have been a few field trials, but most data from them are held within the companies. The limited public data from these field trials were published for the Bakken [15] and the Eagle Ford [16], but many of the data were not available, such as bottom hole flowing pressures, injection rates/pressures, and producing gas-oil ratios. Therefore, it was difficult to validate the results from the laboratory experiments or the numerical models.…”

A Review of Gas Injection in Shale Reservoirs: Enhanced Oil/Gas Recovery Approaches and Greenhouse Gas Control

“…Overall, most pilots did not have any increase in oil production and, based on the results, recommendations for future IOR pilot projects were proposed by the authors, including drilling additional new wells per pilot for injection, testing injectivity in these unstimulated wells, conducting core flooding experiments, and performing simulations in advance to address issues that may arise during the pilot. Later on, Hoffman [64] evaluated seven single-well and multi-well pilot projects in the Eagle Ford based on the published data by the Texas Railroad Commission (TRC). For these cases, lean natural gas or richer hydrocarbon gases were injected in different pilots through a huff-n-puff gas injection scheme.…”