Characterization of small scale heterogeneity to predict acid fracture performance

Oeth, Cassandra; Hill, A.D.; Zhu, Ding; Sullivan, R.B.

doi:10.1016/j.petrol.2013.08.001

Cited by 20 publications

(9 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…During the acid-fracturing process, the matric porosity changed with the dissolution; the number, length, and size of the formed wormhole were hard to determine, which made the leak-off of acids more complicated than hydraulic fracturing; and using a constant injection rate as a substitute for the leak-off of acids was not appropriate. Although most of the acid-fracturing experiments mentioned considering the leak-off of acids, their results did not verify the wormhole development and breakthrough into the cores. ,,,− Based on the previous findings, the leak-off of acids was not explored in this study; however, it should be investigated in future studies.…”

Section: Resultsmentioning

confidence: 86%

“…Although most of the acid-fracturing experiments mentioned considering the leak-off of acids, their results did not verify the wormhole development and breakthrough into the cores. 10 , 11 , 24 , 29 − 31 Based on the previous findings, the leak-off of acids was not explored in this study; however, it should be investigated in future studies.…”

Section: Resultsmentioning

confidence: 99%

“… 7 The measurement method of acid-etched fracture conductivity was introduced in 1968, 8 when Nierode and Kruk put forward an empirical equation for estimation based on their experiments. 9 Laser scanning technology was used to get the accurate morphology after etching, 10 , 11 revealing various mechanisms of an acid–rock reaction. 12 , 13 Meanwhile, innovative testing techniques and further investigations were used to study the factors influencing the acid-etching conductivity.…”

Section: Introductionmentioning

confidence: 99%

“…The measurement method of acid-etched fracture conductivity was introduced in 1968, when Nierode and Kruk put forward an empirical equation for estimation based on their experiments . Laser scanning technology was used to get the accurate morphology after etching, , revealing various mechanisms of an acid–rock reaction. , Meanwhile, innovative testing techniques and further investigations were used to study the factors influencing the acid-etching conductivity. − Cores of different dimensions were used in experiments on acid-etched fracture conductivity: the columnar cores used in the classical N-K experiment were 25.4 mm in diameter and 50.8–76.2 mm in length; , the core used by Ruffet was 100 mm in diameter and 400 mm in length . Antelo and Navarrete in their small-scale core experiment, using a modified API (American Petroleum Institute, which sets some standards for the oil industry) conductivity cell , but with a small size, proposed that representing an accurate heterogeneity of the reservoirs is difficult using small-scale apparatuses.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Large-Scale Acid Fracturing Based on a Large-Scale Conductivity Apparatus

et al. 2021

View full text Add to dashboard Cite

The conductivity of an acid-etched fracture is a necessary indicator for the stimulation of dolomite formation, which affects commercial development. The widely accepted test method involves the use of a small-scale conductivity cell for etching and measuring conductivity. However, the field production reflects that the actual conductivity does not match the measured one and is usually lower. Consequently, the existing studies had limitations and hence the stimulation mechanism needed to be explored further. To understand it more realistically, a novel large-scale apparatus was used in this study to test the conductivity of the acid-etched fracture. The use of this apparatus avoided the near-core excessive eroding and weak heterogeneity with continuous etching in a 1000 mm fracture. The results showed that the conductivity was indeed dissimilar to that in small-scale tests. The morphology of etched large-scale cores featured diversity and complexity, including deep and punctate channels, nonuniform pitting grooves with connected channels, and scale-shaped wavy grooves, which exactly demonstrated the multiple morphology under the influence of carbonate heterogeneity in real reservoirs. Moreover, the effect of increasing injection rate led to the unique etching morphology of scale-shaped wavy and pelviform grooves because of scouring flow and turbulence effects. The degree of surface roughness promoted nonuniform etching along the longitudinal and propagation direction, thus enhancing the conductivity of the whole fracture and confirming that the field treatment limited the pressure rather than the injection rate. The conductivity under different acid type, acid concentration, reaction temperature, and injection rate conditions was lower than that reported, confirming the experimental deviation in small-scale conductivity. The proposed large-scale apparatus test represented the acid-etched fracture conductivity more realistically, thus proving beneficial for the development of carbonate reservoirs.

show abstract

Section: Resultsmentioning

confidence: 86%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Large-Scale Acid Fracturing Based on a Large-Scale Conductivity Apparatus

et al. 2021

View full text Add to dashboard Cite

show abstract

“…Mou 16 builds a 3D steady model and performs an elaborate simulation of acid etching of 3D fractures by solving the 3D flow field on an irregular surface via the finite volume approach. Oeth et al 17 establish the 3D full‐fracture numerical model at the reservoir engineering scale and state in detail how to derive the geostatistical parameters and apply them. The presented methodology can be used for guiding the acid fracturing design.…”

Section: Introductionmentioning

confidence: 99%

Two‐scale continuum model for simulation of acid fracturing in carbonate reservoirs with two main mineral components

Shi

et al. 2022

AIChE Journal

View full text Add to dashboard Cite

To investigate the morphological changes of acid‐etched fractures during acid fracturing in carbonate reservoirs with different mineral compositions, this article develops acid fracturing mathematical models and numerical simulation methods for pore type carbonate reservoirs based on the classic two‐scale continuum model. Practically, these morphological changes of fractures are quantified by characterizing the porosity variation, and different acid‐rock reaction models are built for dolomite and calcite. Compared with physical simulation, the models proposed in the study are accurate in simulating the acid‐etched fracture morphological evolution during acid fracturing. Moreover, efforts are made to evaluate numerical simulation results of acid fracturing in reservoirs with different mineral contents under conditions of different acid pump rates and concentrations. It is recommended to apply higher pump rates and lower acid‐rock reaction rates in reservoirs with higher calcite contents, while lower pump rates and higher acid‐rock reaction rates are recommended for reservoirs with higher dolomite contents.

show abstract

A method for predicting fracture conductivity based on three‐dimensional spatial morphology features

Fei,

Junhai,

Yishan

2023

Energy Science & Engineering

View full text Add to dashboard Cite

The distribution of fracture clearance is an important factor that determines the conductivity of carbonate fractures. In this paper, the morphological analysis of acid fractures and the evaluation of acid fracture conductivity were carried out to test the characteristics of acid fracture clearance and the conductivity of acid fractures under the conditions of different acid rock reaction rates. Combined with the distribution rule of fracture clearance and the calculation formula of acid fracture conductivity under closure stress, the calculation formula of acid fracture conductivity of carbonate rocks is established and verified, and the influence rule of the distribution of fracture clearance on the conductivity of acid fractures is simulated and calculated. The results show that with the increase of the closure pressure, the conductivity of the fracture with a closure pressure of 60 MPa is about 94% lower than that of the fracture with a closure pressure of 10 MPa. The increase in acid dissolution rate is beneficial to improve the fracture conductivity under various closure stresses, and the acid dissolution is beneficial to reduce the influence of the closure stress on the fracture conductivity of acid dissolution. When the confining pressure is 10 MPa, the acid corrosion rate increases from 0.0001 to 0.0004 g/cm2 s, and the conductivity of the acid corrosion fracture increases from 27 to 420 μm2 cm. As the dissolution rate of acid solution increases, the proportion of large clearance on the fracture surface increases, the average value of total clearance increases, and the proportion of contact on the fracture surface decreases.

show abstract

Characterization of small scale heterogeneity to predict acid fracture performance

Cited by 20 publications

References 28 publications

Large-Scale Acid Fracturing Based on a Large-Scale Conductivity Apparatus

Large-Scale Acid Fracturing Based on a Large-Scale Conductivity Apparatus

Two‐scale continuum model for simulation of acid fracturing in carbonate reservoirs with two main mineral components

A method for predicting fracture conductivity based on three‐dimensional spatial morphology features

Contact Info

Product

Resources

About