Unconventional/complex reservoirs

Unconventional and Tight Reservoirs

Applications of particular interest are those addressing challenging well-production needs such as reducing or eliminating liquid loading in gas wells; restimulating existing, underperforming wells, including as an alternative to new well drilling and completion; and remediating water blocking and condensate buildup, both of which can severely impair production from gas wells.

Unconventional intro with abstract background

As unconventional oil and gas fields mature, operators and service providers are looking toward, and collaborating on, creative and alternative methods for enhancing production from existing wells, especially in the absence of, or at least the reduction of, new well activity. While oil and gas price environments remain uncertain, recent price-improvement trends are supporting greater field testing and implementation of innovative applications, albeit with caution and with cost savings in mind. Not only is cost-effectiveness a requirement, but cost-reducing applications and solutions can be, too.

Of particular interest are applications addressing challenging well-production needs such as reducing or eliminating liquid loading in gas wells; restimulating existing, underperforming wells, including as an alternative to new well drilling and completion; and remediating water blocking and condensate buildup, both of which can impair production from gas wells severely. The three papers featured this month represent a variety of applications relevant to these particular well-production needs.

The first paper presents a technology and method for liquid removal to improve gas production and reserves recovery in unconventional, liquid-rich reservoirs using subsurface wet-gas compression. Liquid loading, a recurring issue downhole, can severely reduce gas production and be costly to remediate repeatedly, which can be required. This paper discusses the full technology application process and the supportive results of the first field trial conducted in an unconventional shale gas well.

The second paper discusses the application of the fishbone stimulation system and technique in a tight carbonate oil-bearing formation. Fishbone stimulation has been around for several years now, but its best applications and potential have not necessarily been fully understood in the well-stimulation community. This paper summarizes a successful pilot application resulting in a multifold increase in oil-production rate and walks the reader through the details of the pilot candidate selection, completion design, operational challenges, and lessons learned.

The third paper introduces and proposes a chemical treatment to alleviate phase trapping in tight carbonate gas reservoirs. Phase trapping can be in the form of water blocking or increasing condensate buildup from near the wellbore and extending deeper into the formation over time. Both can reduce relative permeability to gas severely. Water blocks can be a one-time occurrence from drilling, completion, workover, or stimulation operations and can often be treated effectively with solvent plus proper additive solutions. Similar treatments for condensate banking in gas wells, however, can provide only temporary alleviation, if they are even effective. This paper proposes a technique for longer-term remediation of phase trapping in tight carbonate gas reservoirs using a unique, slowly reactive fluid system.

This Month’s Technical Papers

Fishbone Stimulation Enhances Tight Carbonate Productivity

Technique Proves Effective in Remediation of Phase-Trapping Damage in Tight Reservoirs

Subsurface Compressor System Improves Gas Production in Unconventional Reservoirs

Recommended Additional Reading

SPE 200345 Insights Into Field Application of Enhanced-Oil-Recovery Techniques From Modeling of Tight Reservoirs With Complex High-Density Fracture Network by Geng Niu, CGG, et al.

SPE 201413 Diagnostic Fracture Injection Test Analysis and Simulation: A Utica Shale Field Study by Jeffery Hildebrand, The University of Texas at Austin, et al.


Leonard J. Kalfayan, SPE, is a principal adviser and technical authority for production engineering and stimulation with Hess Corporation in Houston. He has 40 years of experience in the oil, gas, and geothermal industries. Kalfayan’s background is in production enhancement, new technology development and implementation, global technical support, and business development. Before joining Hess in 2009, he worked for the Union Oil Company of California and BJ Services and as an industry consultant. Kalfayan was a 2005 SPE Distinguished Lecturer and a 2013 SPE Distinguished Member. He has served on several SPE program and technical committees. Kalfayan is author of more than 30 SPE and other journal publications and holds 13 US patents. He is also author of the book Production Enhancement With Acid Stimulation, now in its second edition; coauthor of the book The Energy Imperative; and coeditor of the SPE monograph Acid Stimulation. He is a member of the JPT Editorial Review Committee and can be reached at lkalfayan@hess.com.