Embedment and Fracture Conductivity in Soft Formations Associated with HEC, Borate and Water-Based Fracture Designs

Lacy, L. L.; Rickards, Allan; Ali, Syed F.

doi:10.2523/38590-ms

Cited by 15 publications

(15 citation statements)

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“…There have been many studies related to fracture conductivity and the parameters affecting its performance. Lacy et al (1997) did experimental research on embedment and fracture conductivity in soft formations. They learned that embedment is affected mainly by rock type, closure stress, proppant size, strength, concentration and distribution.…”

Section: Fracture Conductivitymentioning

confidence: 99%

The Effect of Rock Properties on Fracture Conductivity in the Marcellus Shale

Pena

Zhu

Hill

2016

Day 1 Wed, August 24, 2016

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The success of fracture stimulations depends on the ability to fracture the rock and to maintain fracture conductivity. Therefore, in order to have a successful treatment, the effect of rock and proppant characteristics should be understood. This paper investigates the relationship between fracture conductivity and rock properties for two different locations in the Marcellus shale. In this work, a series of experiments were performed in order to better understand the mechanical behavior of the Marcellus Shale. Multiple cores from Allenwood and Elimsport locations in Pennsylvania were collected to ensure repeatability in the results. The core samples were cut parallel and perpendicular to the bedding planes in order to analyze the effect of anisotropy in fracture conductivity. Additionally, compressive triaxial tests were performed to obtain the rock mechanical properties such as Young's Modulus, Poisson's Ratio and Ultimate Compressive Strength, and X-ray Diffraction analysis was used to obtain mineralogy composition. The laboratory results were carefully compared with previous fracture conductivity data and surface roughness data from the same Marcellus shale locations where proppant concentration was kept constant to reduce the variables affecting the fracture conductivity behavior. The findings showed that the anisotropy effect is present for this formation and reflected in the fracture conductivity values, where samples parallel to the bedding plane seem to have higher Young's Modulus. It was confirmed that at proppant monolayer concentration the main mechanism for conductivity loss is proppant embedment, where due to the high localized stress, the rock-proppant interaction goes directly to permanent deformation of the rock. It was also observed that a higher Young's Modulus helps to maintain the fracture width which translates in lower rate of conductivity loss with increasing closure stress, therefore, rock mechanical properties have impact on fracture conductivity. The phenomenon observed is less pronounced if a multilayer proppant concentration is used, where the proppant pack characteristics become an important parameter in fracture conductivity. In this paper, we present an analysis of the effect of rock properties in the fracture conductivity behavior based on a series of experimental results from the Marcellus Shale, where the role of permanent deformation was taken into consideration as a parameter causing fracture conductivity lost. This is the first time the effect of rock characteristics in fracture conductivity is analyzed based on experimental work for the Marcellus shale.

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Section: Fracture Conductivitymentioning

confidence: 99%

The Effect of Rock Properties on Fracture Conductivity in the Marcellus Shale

Pena

Zhu

Hill

2016

Day 1 Wed, August 24, 2016

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“…The fines that are created through proppant crushing can accumulate on the fracture face causing additional loss of the fracture conductivity. Lacy et al, (1997) stated in their studies that proppant packs are significantly damaged due to formation fines caused by embedment. Figure 2.6 shows a representation of how proppants can be embedded into the formation downhole.…”

Section: Embedmentmentioning

confidence: 99%

Fracturing Fluid Effects on Young's Modulus and Embedment in the Niobrara Formation

2014

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New discoveries of shale plays and their abundant resources have directed the petroleum industry towards their development. Production from shale reservoirs has grown significantly in the past few decades spurred by successful development of plays such as the Barnett and Bakken Shales. Due to their low permeability, hydraulic fracturing is a necessity for economic production in these reservoirs, and the success of these reservoirs is dependent on optimizing hydraulic fracturing designs which are in turn dictated by an understanding of the mechanical properties of these reservoirs. The geometric growth and conductivity of fractures in these reservoirs are influenced by many factors. Young's modulus reduction, which essentially means weakening of the formation, is one of these factors. This reduction damages the reservoir and makes embedment of proppants into the fracture face a detrimental effect on fracturing success. The goal of this research project is to focus on how different fracturing fluids change the Young's modulus of the Niobrara shale and how this change affect the proppant embedment and conductivity when commonly used proppants are subjected to pressure tests in the effected Niobrara shale samples.A series of tests and associated methodology were developed and applied to investigate how the Niobrara shale's Young's modulus is affected by various fracturing fluids and to quantify associated proppant embedment. In order to achieve this, core samples at various depths from the same well were selected from the cores. The selection was made based on mineralogy data. Samples containing the highest, lowest, and median calcite percentage and porosity were selected to be imaged with QEMSCAN in order to understand the mineralogy of the samples being used. Eight selected samples were then saturated with four fracturing fluids (freshwater, KCl, KCl+friction reducer, and freshwater+KCl substitute). Four of these samples were the "expansion" samples to see if the results were more dependent on the fluid selections. Two additional samples were heated with freshwater and KCl at 180°F for five days to investigate the heat effect on Young's modulus and embedment in comparison to room iv temperature experiments. In order to compare in-situ saturated Young's modulus values to dry Young's modulus values of cores obtained by nanoindenter, the Gassmann fluid substitution equation was used.This method showed significant Young's modulus difference between in-situ saturated and dry core values.The saturated/room temperature and saturated/heated cores were then subjected to 3030 psi for one hour while selected proppants were placed in between them. Four different proppant types (16/30 Brady, 20/40 Ottawa, 20/40 Ceramic, and 20/40 RCS) were used in this research. Various combinations of cores affected by fluids and proppants were made in order to simulate actual treatment designs. The cores were also scanned by scanning acoustic microscope (SAM) before and after they were subjected to pressure with proppants, so that...

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“…Previous studies have shown that proppant embedment can reduce fracture aperture by between 10 and 60%. This leads to a loss in the productivity, since a reduction of the fracture aperture by just 20% can restrict the fluid flow and recovery by up to 50% (Lewis L. Lacy, Rickards, & Ali, 1997).…”

Section: Proppant Embedment Processmentioning

confidence: 99%

Indentaion Hardness for Improved Proppant Embedment Prediction in Shale Formations

Mueller

Amro

2015

All Days

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The aim of hydraulic fracturing is the generation and maintenance of highly permeable pathways. To achieve this, a high hydraulic pressure is applied to overcome the breakdown pressure in developed formations. To avoid the closure of the generated fractures due to the acting in-situ stress in the subsurface, proppantsareused. The hydraulic conductivity (C f ) of such a fracture is defined as the permeability of the proppant pack (k pr ) times the fracture width (w f ). However, this value cannot be considered a constant. The increasing effective pressure leads to an increased stress on the proppants, thus increasing their embedment into the formation surface. Such a situation becomes particularly critical in weak formations and in formations where the interaction between the frac fluid and the formation can lead to a change in the mechanical properties in the fracture face. This paper will present an approach to model the embedment of various kinds of proppant packs with respect to the proppant size distribution and the proppant density. This approach uses the indentation hardness of the surface formation to calculate the embedment. The advantage of this parameter, which can be measured by applying the hardness test according to Brinell, is that it describes the mechanical properties of the surface of the formation. This area, which is highly influenced by the treatment fluid, can show great differences in the mechanical behavior compared to the untreated area. This can lead to an under-or overestimation of the embedment, since the mechanical parameters normally used for calculation are measured on core samples representing the mechanical behaviour of the untreated rock mass. The consideration of the indentation hardness can lead to a more accurate embedment prediction, since it describes the behaviour of the first 0.1-2 mm of a surface, in which the embedment alone can lead to a closure of a fracture. The first series of hardness tests according to Brinell, conducted on different shale types, have proven that the fluid composition affects the indentation hardness of the samples, which will of course affect the depth of the embedment. The measurements are the basis for the embedment modelling which will be presented in this article.

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Embedment and Fracture Conductivity in Soft Formations Associated with HEC, Borate and Water-Based Fracture Designs

Cited by 15 publications

References 0 publications

The Effect of Rock Properties on Fracture Conductivity in the Marcellus Shale

The Effect of Rock Properties on Fracture Conductivity in the Marcellus Shale

Fracturing Fluid Effects on Young's Modulus and Embedment in the Niobrara Formation

Indentaion Hardness for Improved Proppant Embedment Prediction in Shale Formations

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