Hydraulic Fracturing Critical Design Parameters in Unconventional Reservoirs

Abstract

Horizontal well drilling and hydraulic fracturing have become the enabling technologies for unconventional reservoir development. From tight gas, to oil and gas-producing shales and coal bed methane, all these resources rely on hydraulic fracturing for its commercial viability. The primary goal of the completion in these ultra-low permeability formations is to provide a conductive path to contact as much rock as possible, through the use of multistage hydraulic fractures along a horizontal lateral. Reservoir contact is optimized by defining the extent of the lateral length, the number of stages to be placed in the lateral, the fracture placement technique and job size. Fracture conductivity is determined by the proppant type and size, fracturing fluid system as well as the placement technique. While most parameters are considered in great detail in the completion design, the fracture conductivity receives lesser attention. On one side many feel that in extremely low permeability formations hydraulic fractures act as ‘infinitely conductive features’, even with minimal conductivity. On another side many factors that affect the effective conductivity acting in the hydraulic fracture are poorly understood or overlooked. This can lead to a disappointing outcome with wells producing below the reservoir potential. This paper presents a technique to assess the realistic fracture conductivity at downhole conditions, describe the relationship between conductivity and productivity and its economic implications in proppant selection. The effects of transverse fractures, low areal proppant concentration and flow dynamics, are also considered among other variables. Fracture modeling and actual field results will be presented to illustrate the optimization process. The case histories included in the paper show the successful implementation of this method in shale gas and liquids rich formations.

Review of the Development Status and Technology of Tight Oil: Advances and Outlook

“…Tight oil resources are mainly distributed along the Rocky Mountains and Appalachian Mountains. − The United States is currently the most successful country in extracting tight oil . Since the comprehensive application of horizontal well staged fracturing technology in 2006, the development of tight reservoirs has promoted the recovery of the North American oil supply. − At present, the main tight oil producing areas in the United States include the Bakun Formation, Naiebral, Barnett, and Eagle Beach tight oil areas. In 2023, the production of these four tight oil zones reached over 30 million tons (Table ).…”

Efficient Use of Data Analytics in Optimization of Hydraulic Fracturing in Unconventional Reservoirs

“…Holditch (2006) defines the tight gas reservoirs as, ЉThe reservoirs that cannot be produced at economic flow rates nor recover economic volumes of natural gas unless the well is stimulated by a large hydraulic fracture treatment or produce by use of horizontal wellbore or multilateral wellbores.Љ The same definition can be used for all the unconventional resources. Primary aim of stimulation treatment is to provide a conductive path for flow and by lateral wells increase the contact area for the production (Saldungaray et al 2013). The optimum design of drilling, completion, and stimulation methods depend on the reservoir characteristics and economics.…”

Proppants Selection Based on Field Case Studies of Well Production Performance in the Bakken Shale Play

“…It is widely accepted that the conductivity of proppants plays an important role on the production performance of wells (Saldungaray et al 2013, Vincent 2002. Regardless of rock type, ceramic proppant exhibited the highest conductivity, followed by resin coated sand, which was followed by silica sand.…”