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Apparatus for Dynamic Fluid Loss Testing

IP.com Disclosure Number: IPCOM000239521D
Publication Date: 2014-Nov-13
Document File: 8 page(s) / 243K

Publishing Venue

The IP.com Prior Art Database

Abstract

Fluid leak off in a hydraulic fracturing treatment is inevitable although its severity can be controlled. Estimation of fluid leak off rates is essential since it is one of the most important variables for successful design and placement of fracturing fluids. Volume of fluid lost determines the fluid efficiency and affects the treatment size and proppant scheduling. This paper discusses the design and construction of a robust maintenance-friendly and highly cost effective apparatus for dynamic fluid loss testing that closely simulates downhole conditions. This apparatus gives provision to test three cores of different permeability’s at the same time. The cell can accommodate cylindrical cores of 1.5 inches and higher. Such large sized cores negate the Darcy effects observed in small diameter cores (15/16 or 1 inch), while providing adequate surface area to improve accuracy.

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Apparatus for Dynamic Fluid Loss Testing

Abstract

Fluid leak off in a hydraulic fracturing treatment is inevitable although its severity can be controlled. Estimation of fluid leak off rates is essential since it is one of the most important variables for successful design and placement of fracturing fluids. Volume of fluid lost determines the fluid efficiency and affects the treatment size and proppant scheduling. This paper discusses the design and construction of a robust maintenance-friendly and highly cost effective apparatus for dynamic fluid loss testing that closely simulates downhole conditions. This apparatus gives provision to test three cores of different permeability's at the same time. The cell can accommodate cylindrical cores of 1.5 inches and higher. Such large sized cores negate the Darcy effects observed in small diameter cores (15/16 or 1 inch), while providing adequate surface area to improve accuracy.

Introduction

Estimating fluid leak off rates during hydraulic fracturing requires a thorough understanding of filtration mechanism by laboratory experiments. Fluid leak-off of fracturing fluids is controlled by build-up of a filter cake as fluid passes into the core matrix leaving a very low permeability polymer mass near the fluid rock interface [3].

The most commonly used method for studying the fluid loss is a static test in which fluid does not move past the core face. Static testing, as per API RP-39 [1] procedures allow the filter cake to continually increase in thickness throughout the duration of the fluid leak off test. However, these tests are not representative of the actual field conditions where the fluid flows past the filter cake limiting the growth of filter cake to some equilibrium thickness. Under dynamic conditions, the growth of filter cake is affected by several factors such as fluid velocity, fluid loss additive, polymer type, fluid viscosity, pressure differential, relative permeability etc. Thus, the dynamic test provides a closer resemblance to actual field conditions.

Shear rates equivalent to typical fracture flow conditions have been found to provide a comparative basis for the effects of fluid velocity on filter cake erosion under different gap widths. This led to the development of slot flow type test cells [2].

Scope

Penny [2] first referenced the use of two 10-in2 elongated core wafers mounted in a modified API conductivity cell to measure leak off. The modified API conductivity cell has since been widely used to conduct the dynamic fluid loss test. Some of the disadvantages of using the API cells as per the authors' opinion are as follows:

• Only single permeability core can be tested at a time (usually Ohio Sandstone);

• The core wafer is rectangular with half circle in its side thereby making core cutting difficult;


• A single cell occupies lot of space;

• Time required to conduct a single test is higher; and,

• Flushing, washing and maintenance during or after compl...