The evolution of horizontal drilling and multistage completions has changed matrix stimulation from the “more acid, better result” belief to effective lateral distribution and deeper penetration with less acid.
Large-gallon-per-foot-based treatment became impractical and unnecessary. The constant remains that drilling is blamed for causing formation damage; therefore, matrix stimulation is needed. Underbalanced coiled-tubing drilling aimed at changing this constant, however, has its own drawbacks.
For certain lithologies, acid tunneling can be an attractive alternative to rotary-bit drilling. Though the technology was proposed many years ago, its use has been limited. Hardware to control the drilling direction, fluids to dissolve the formation rock efficiently, and jetting dynamics to optimize the rate of penetration have been pushed forward progressively. The goal of stimulation while drilling finally may be achievable.
Of course, not all reservoir rock types are readily soluble in chemicals. Cracking the reservoir rock will continue to be the preferred process for sandstone. The first mechanism we think of for rock cracking is hydraulics. Unless full-fledged hydraulic fracturing is required, using high-energy pulses induced by propellant or other chemical reactions can produce sufficient pressure to break the rock past the near-wellbore formation damage. Perfecting the control and job design can lead to efficiency and broader implementation.
One question we often ask in the matrix-stimulation domain is “what’s new?” It almost seems that the products and technologies of yesterday have been brought out again and again with minor twists. Indeed, it is amazing how many “new technologies” actually have been around for decades.
While most of the industry is busy handling daily operations and logistics, it is encouraging to see universities, government-supported research and development institutes, and even some large service and operating companies studying the science behind the products and technologies. Advanced multiscale, multiphysics mathematical models are used to optimize particle bridging for diverting efficiency; large-scale experimental setups are used to gain insights into differential etching patterns during acid fracturing caused by viscous fingering and heterogeneous reactions, perforation penetration in realistic geometry and stresses, and other phenomena that could not be observed by small-scale laboratory testing. These studies help us appreciate the ingenuity of our predecessors and help us fit the technologies to the right applications better.
This Month's Technical Papers
Recommended Additional Reading
SPE 185344 Application of Closed-Fracture Acidizing for Stimulation of Tight Carbonate Reservoir in Mumbai Offshore by Dilip Kumar Sarma, Oil and Natural Gas Corporation, et al.
SPE 187019 Large-Scale Visual Experiment and Numerical Simulation of Acid Fingering During Carbonate Acid Fracturing by Xiaogang Li, Southwest Petroleum University, et al.
SPE 189546 Influence of Transport Conditions on Optimal Injection Rate for Acid Jetting in Carbonate Reservoirs by Dmitry Ridner, Texas A&M University, et al.
Frank Chang, SPE, Petroleum Engineering Consultant, Saudi Aramco
01 June 2018
SPE Talks To: Mathias Carlsen
In this episode, we discuss the state of shale EOR in the US and what hydrocarbon producers need to know about seperator oil shrinkage.
The bulk of the literature on enhanced oil recovery from the past year has been devoted to an improved understanding of trends started more than a decade ago with physical and numerical modeling.
Study Investigates Smart Waterflooding in Sandstone Reservoirs
In this paper, the authors consider the effect of water chemistry on water/rock interactions during seawater and smart waterflooding of reservoir sandstone cores containing heavy oil.
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