HYDRAULIC FRACTURE CONDUCTIVITY

Hydraulic fracture conductivity

Hydraulic fracture conductivity

Introduction

As reported in J.B. Clark's Standolind Oil Company publication on hydraulic fracturing, retaining conductivity of the created fracture is an important part of the process. One of process requirements suggested by Clark J.B. was that the hydraulic fracturing fluid be able to carry a propping agent in suspension, such as sand so that as the fracture closes a conductive flow channel will remain. Another requirement was that the fracturing fluid be sufficiently thin after the job that it will flow out of the fracture and not stay in place and plug the fracture it formed. Many improvements have been made in the hydraulic fracturing process over the last 60 years. Improving fracture conductivity by improving propping agents and fracturing fluids has been part of this improvement evolution. Over the years a large amount of work has gone into the research and development of fracturing fluids that minimize the damage to the proppant pack created by the fracturing fluid. Some of the significant developments through the years include the use of derivatized guars, lower polymer concentrations, viscoelastic technology, fiber transport and encapsulated breakers. The next big step change in the fracturing process involving proppant technology was Exxon Company's 1977 publication on the use of sintered bauxite as a propping agent(Cooke, Claude E. et al.). Exxon performed 17 field tests using the sintered bauxite material in wells with depths ranging from 10,000 ft to 16,000 ft. Based on the results, the company concluded that substantial economic benefit could be obtained with this new proppant. The use of ceramic proppants in the hydraulic fracturing market over 30 years later is widespread and a well accepted technology in the industry (Moraa, Orogbemia, Karpyna, 2010).

Hydraulic fracturing Conductivity

Hydraulic fracturing has been proven to be one of the most effective techniques for improving the productivity of dry gas reservoirs. Acid fracturing and hydraulic fracturing have also found to be effective in improving the productivity of gas condensate reservoirs. Hydraulic fracturing in gas condensate reservoirs also has additional advantages: stimulation reduces the pressure drawdown and thus leads to less liquid dropout. Distribution of the liquid condensate around the fracture, whose length can be several hundred feet for low permeability reservoirs but only tens of feet for high-permeability reservoirs, can alleviate or greatly soften the impact of hydraulic fracturing on gas production.

Proppant Wettability

Wettability is defined as “the tendency of one fluid to spread on, or adhere to a solid surface in the presence of other immiscible fluids”. The fluid with the higher affinity toward the solid surface is called the wetting phase, the other fluid is called non-wetting. Wettability is a very important concept in oil recovery processes and has a strong impact on distribution, location and flow of oil and water in reservoir during production. In a water-wet system, water will occupy the narrowest pores and will be present as a film on the pores wall while oil will reside as oil droplets in the middle of the ...