ABSTRACT
Shale gas is natural gas extracted from oil shale rock formations, or plays, located deep below the surface of the earth. The amount or magnitude of shale gas reserves available under the earth’s surface is very vast and extremely difcult to estimate. It has long been known that natural shale gas and shale oil reserves were deposited and trapped in hard dense shale rocks formed from ancient ocean basins several hundred million years ago. Until recently, the oil shale resources that were economically useful, technologically feasible, and environmentally manageable had been limited to the oil shale deposits that are shallow and more easily approachable from the earth’s surface. In other words, we did not have all the enabling technologies and machineries to be able to tap the resources that are trapped very deep under the terrain surface. Initially, most efforts in commercial oil shale utilization were focused on shale natural gas production. The popularly used terminology “shale gas” is reecting this trend and historic event. However, increasingly more efforts have been spent
9.1 What Is Shale Gas? ....................................................................................... 311 9.2 Background Information............................................................................... 312
9.2.1 Distribution of Shale Gas and Shale Oil Deposits ............................ 312 9.2.2 Commercially Noteworthy Shale Deposits in the United States ...... 315 9.2.3 Difference between Technically Recoverable and Economically
Available Resources .......................................................................... 316 9.2.4 Remarkable Speed of Commercial Development ............................. 317
9.3 Hydraulic Fracture Technology .................................................................... 318 9.3.1 What Is Hydraulic Fracture? ............................................................. 318 9.3.2 How Is Hydraulic Fracture Done? .................................................... 318 9.3.3 Chemicals and Additives for Hydraulic Fracture Fluids .................. 320 9.3.4 Proppant Sand ................................................................................... 324 9.3.5 Frac Water ......................................................................................... 325 9.3.6 Flowback Water Control and Management ...................................... 326
9.4 Environmental Considerations ..................................................................... 327 9.5 Future Research and Development Needs .................................................... 328 References .............................................................................................................. 329
in oil-focused drilling for production of shale crude oil, as well evidenced in North Dakota, United States. To distinguish the crude oil product extracted from oil shale deposits, people use the terminology “shale fuel,” which includes both gas and liquid products, or “shale oil crude,” which is only for the liquid product.
