Abstract

Operative and economical optimization of hydraulic fracture stimulation designs requires accurate reservoir description.

For unconventional tight gas reservoirs is it commonly difficult obtain reliable results from conventional build up analysis after flow testing a well because the time required to reach the IARF (Infinite Acting Radial Flow) could be much longer than normal rig time operations will practically allow. In many cases the impossibility of the well to produce after perforation makes the scenario even worst.

Mini-Fall-Off injection test is economical and efficient technical solution to solve this problem providing an excellent starting point to understand unconventional plays and optimize the entered process of hydraulic fracturing technique.

The scope of this work is to present an optimal operative processes which allow understand how, when and where is recommended apply this technology giving a key point to optimize the hydraulic fracture stimulation. Following a theoretical description to this new methodology is provided.

In addition, this work includes a detailed guideline for planning execution and interpretation of the falloff pressure to obtain reliable reservoir transmissibility, reservoir pressure and closure pressure.

Finally, the results of two cases were evaluated and it was determined that a simple field implementation could be adopted as a standard to be used in conventional pre-frac pumping procedures.

Introduction

During the last sixty years the main role of hydraulic fracturing technology was changing as a result of necessity and theoretical knowledge. The concept of "Fracturing to Past Damage" (1945–1975) found the main application on mili-D environments and was the first concept to understand how the frac works. On the 80' the concept of "Massive Hydraulic Fracturing" (1975–1990) was developed with great results for tight gas reservoirs. For medium and high perm reservoir "Tip Screen Out" technique seems to be the best solution from the 90' up to now. In the 2000 year unconventional reservoir start extensively treated with "water Frac" techniques. Near future of hydraulic fracturing is growing as a merge between reservoir engineering and stimulation engineering and this is main reason to understand that each shut it, after production or injection, with or without fracture in which is possible reach pseudo radial flow could gives good approximation of some reservoir information as permeability and pressure. The main parameter to optimize hydraulic fracture is the reservoir permeability almost never known for unconventional reservoirs.

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