Acid-Fracture Conductivity Correlation Development Based on Acid-Fracture Characterization

Pournik, Maysam; Zhu, Ding; Hill, A.D.

doi:10.2118/122333-ms

Cited by 27 publications

(14 citation statements)

References 24 publications

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“…These images can show details that would not be perceived at naked eye. In addition, they can help to characterize the different etching patterns as defined elsewhere (Antelo et al, 2009;Pournik et al, 2009) namely channels, roughness, cavity, uniform and turbulent. These images are in the companion paper (Neumann et al, 2012).…”

Section: Methodsmentioning

confidence: 99%

Building Acid Frac Conductivity in Highly-Confined Carbonates

et al. 2012

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The deep and hard limestones found off-shore Brazil are being extensively evaluated, and some of them would require stimulation to enable commercial development. The main objective of this paper is to discuss the feasibility of acid fracturing stimulation in hard carbonates. Laboratory test are performed to verify whether an acid-induced fracture can withstand the high effective normal stresses expected during the exploitation stage of pre-salt development, keeping an acceptable conductivity. There is no agreement in the technical community regarding the survival of an acid fracture at closure stress greater than 5,000 psi. However, the experience that leads to this controversy is mainly based on: (1) wells on land and, (2) few published tests on rocks with mechanical properties compatible with those depths. An experimental program has been designed to evaluate these chances of acid fracture survival. A few initial essays with samples of these carbonate rocks have shown significantly higher rock strength than those commonly found in the literature. Initially, the Nierode & Kruk correlation (1973) is used to predict fracture conductivity behavior. Both mechanical strength and dissolved rock equivalent conductivity are measured from outcrops, and from soft and hard offshore carbonates samples. This work reports the results with outcrops and reservoir samples, in order to assess whether the adopted experimental methodology is consistent and reproducible. Some topics about acid fracture conductivity prediction are also addressed. Further research should be performed with pre-salt rock samples using the same procedures. IntroductionOpen and conductive acid fractures are difficult to obtain. The existence of such fracture depends on the resistance of their asperities, ridges, hills and valleys to avoid being overwhelmed by the rock that surrounds it. Could the Argonauts feat be replicated and an acid fracture is maintained always open? According to myth, the passage of the Argonauts on Argó through the Symplegades, the clashing rocks, anchored and kept these rocks forever open in the Bosphorus strait. The analogy with an acid fracture is direct. Unfortunately maintain an acid fracture always open is also a myth. Sometimes, acid fractures close.

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Section: Methodsmentioning

confidence: 99%

Building Acid Frac Conductivity in Highly-Confined Carbonates

et al. 2012

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“…Acid fracturing is a well stimulation technology for carbonate reservoirs that requires uneven dissolution of the rock fracture face (Antelo et al, 2009;Malagon et al, 2006;Pournik et al, 2009;Ruffet et al, 1997). In the acid fracturing process, a fracture is created with hydraulic pressure and the acid dissolves rock along the faces of the fracture.…”

Section: Acid Fracturing Reviewmentioning

confidence: 99%

“…No conductivity correlation accurately predicts acid fracture conductivity at reservoir scale despite the theoretical and experimental work on the subject (Gangi, 1978;Gong et al, 1999;Mou et al, 2010;Nierode and Kruk, 1973;Pournik et al, 2009;Walsh, 1981). The most widely used correlation was developed by Nierode and Kruk (1973) and is based on experimental data on acid fracture conductivity from laboratory tests.…”

Section: Acid Fracturing Reviewmentioning

confidence: 99%

“…Acid fracture conductivity is dependent on surface etching patterns, which are determined by the distribution of permeability and mineralogy along the fracture face (Deng et al, 2009;Malagon et al, 2006;Mou et al, 2009;Pournik et al, 2009). An accurate prediction of acid fracture conductivity therefore necessitates the detailed description of the acid etching profile on each fracture surface, which depends on acid transport in the fracture, leakoff due to local permeability, and acid/rock reactions.…”

Section: Acid Fracturing Reviewmentioning

confidence: 99%

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Characterization of small scale heterogeneity to predict acid fracture performance

Oeth¹,

Hill²,

Zhu³

et al. 2013

Journal of Petroleum Science and Engineering

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“…In addition, they can help to characterize the different etching structures defined as channels, roughness, cavity, uniform and turbulent (Antelo et al, 2009;Pournik et al, 2009). …”

Section: The Laser Scanner Recorded Surface Profiles Before and Aftermentioning

confidence: 99%

Acid Fracturing: New Insigths on Acid Etching Patterns from Experimental Investigation

et al. 2012

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Nowadays, it is commonplace to say that acid fracture conductivity depends on the fracture face asperities. Does it really depend on it? Almost thirty years ago, someone wrote, "We believe the conductivity measured in these tests is mainly due to the smoothing of peaks and valleys on the rough fracture faces, and is independent of rock heterogeneities due to the small sample size." Moreover, almost one year ago, one wrote, "More asperities touch and deform as the closure stress increases. The channels become even shorter and fewer openings are left." Between these two extremes, the asperities came to be pointed out as an essential factor to generate acid conductivity. Many published results from small, wet sawed and leveled carbonate rock samples support such claim. We did the same. Our experimental investigation on small scale carbonate samples with sawn faces, both from outcrops and well cores, reconfirm the existence of three main acid patterns namely uniform, channels and roughness. The design of experimental apparatus prevented that those etching patterns were artifact patterns. The acid etching patterns determine different conductivity behavior under confining stress. However, hydraulic fractures are tensile fractures and they are naturally rough. In nature, there is no such thing as a leveled fracture face. Tensile fracture faces could be rougher than fracture face after acid reaction. In fact, the first experimental results show that after acid reaction, linear roughness of tensile fractures can be larger, equal or less than linear roughness before acid reaction. This paper presents experimental results and discusses the asperities paradigm.

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Acid-Fracture Conductivity Correlation Development Based on Acid-Fracture Characterization

Cited by 27 publications

References 24 publications

Building Acid Frac Conductivity in Highly-Confined Carbonates

Building Acid Frac Conductivity in Highly-Confined Carbonates

Characterization of small scale heterogeneity to predict acid fracture performance

Acid Fracturing: New Insigths on Acid Etching Patterns from Experimental Investigation

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