Hydraulic Fracturing Optimization for Unconventional Reservoirs - The Critical Role of the Mechanical Properties of the Natural Fracture Network

2012 ◽  
Author(s):  
Neal Borden Nagel ◽  
Marisela Sanchez-Nagel ◽  
Byungtark Lee ◽  
Xavier Garcia
Keyword(s):  
Mechanical Properties ◽  
Hydraulic Fracturing ◽  
Critical Role ◽  
Fracture Network ◽  
Natural Fracture ◽  
Unconventional Reservoirs

The Critical Role of In-Situ Pressure on Natural Fracture Shear and Hydraulic Fracturing-Induced Microseismicity Generation

2013 ◽  
Author(s):  
F. Zhang ◽  
Neal Borden Nagel ◽  
Marisela Sanchez-Nagel ◽  
Byungtark Lee ◽  
Alireza Agharazi
Keyword(s):  
Hydraulic Fracturing ◽  
Critical Role ◽  
Natural Fracture

scholarly journals A new slick water system for hydraulic fracturing in tight reservoir to enhance imbibition oil recovery

2021 ◽  
Vol 303 ◽  
pp. 01001
Author(s):  
Yu Haiyang ◽  
Ji Wenjuan ◽  
Luo Cheng ◽  
Lu Junkai ◽  
Yan Fei ◽  
...  
Keyword(s):  
Contact Angle ◽  
Interfacial Tension ◽  
Hydraulic Fracturing ◽  
Oil Recovery ◽  
Water System ◽  
Natural Fracture ◽  
Fracturing Fluid ◽  
The Core ◽  
Ultralow Permeability

In order to give full play to the role of imbibition of capillary force and enhance oil recovery of ultralow permeability sandstone reservoir after hydraulic fracturing, the mixed water fracture technology based on functional slick water is described and successfully applied to several wells in oilfield. The core of the technology is determination of influence factors of imbibition oil recovery, the development of new functional slick water system and optimization of volume fracturing parameters. The imbibition results show that it is significant effect of interfacial tension, wetting on imbibition oil recovery. The interfacial tension decreases by an order of magnitude, the imbibition oil recovery reduces by more than 10%. The imbibition oil recovery increases with the contact angle decreasing. The emulsifying ability has no obvious effect on imbibition oil recovery. The functional slick water system considering imbibition is developed based on the solution rheology and polymer chemistry. The system has introduced the active group and temperature resistant group into the polymer molecules. The molecular weight is controlled in 1.5 million. The viscosity is greater than 2mPa·s after shearing 2h under 170s-1 and 100℃. The interfacial tension could decrease to 10-2mN/m. The contact angle decreased from 58° to 22° and the core damage rate is less than 12%. The imbibition oil recovery could reach to 43%. The fracturing process includes slick water stage and linear gel stage. 10% 100 mesh ceramists and 8% temporary plugging agents are carried into the formation by functional slick water. 40-70 mesh ceramists are carried by linear gel. The liquid volume ratio is about 4:1 and the displacement is controlled at 10-12m3/min. The sand content and fracturing fluid volumes of single stage are 80m3 and 2500 m3 respectively. Compared with conventional fracturing, due to imbibition oil recovery, there is only 25% of the fracturing fluid flowback rate when the crude oil flew out. When the oil well is in normal production, about 50% of the fracturing fluid is not returned. It is useful to maintain the formation energy and slow down the production decline. The average cumulative production of vertical wells is greater than 2800t, and the effective period is more than 2 years. This technology overcoming the problem of high horizontal stress difference and lack of natural fracture has been successfully applied in Jidong Oilfield ultralow permeability reservoir. The successful application of this technology not only helps to promote the effective use of ultralow permeability reservoirs, but also helps to further clarify the role of imbibition recovery, energy storage and oil-water replacement mechanism.

scholarly journals Discrete Element Simulation of Interaction between Hydraulic Fracturing and a Single Natural Fracture

Fluids ◽  
2019 ◽  
Vol 4 (2) ◽  
pp. 76
Author(s):  
Basirat ◽  
Goshtasbi ◽  
Ahmadi
Keyword(s):  
Hydraulic Fracturing ◽  
Fractured Reservoirs ◽  
Critical Role ◽  
Injection Pressure ◽  
Discrete Element ◽  
Natural Fracture ◽  
Effective Parameters ◽  
Fracture Geometry ◽  
Interaction Mode ◽  
Element Simulation

Hydraulic fracturing (HF) treatment is performed to enhance the productivity in the fractured reservoirs. During this process, the interaction between HF and natural fracture (NF) plays a critical role by making it possible to predict fracture geometry and reservoir production. In this paper, interaction modes between HF and NF are simulated using the discrete element method (DEM) and effective parameters on the interaction mechanisms are investigated. The numerical results also are compared with different analytical methods and experimental results. The results showed that HF generally tends to cross the NF at an angle of more than 45° and a moderate differential stress (greater than 5 MPa), and the opening mode is dominated at an angle of fewer than 45°. Two effects of changing in the interaction mode and NF opening were also found by changing the strength parameters of NF. Interaction mode was changed by increasing the friction coefficient, while by increasing the cohesion of NF it was less opened under a constant injection pressure.

Dislocations Induced by Heavy Boron Doping of Silicon

1991 ◽  
Vol 49 ◽  
pp. 814-815
Author(s):  
X. J. Ning ◽  
P. Pirouz
Keyword(s):  
Mechanical Properties ◽  
Critical Role ◽  
Boron Doping ◽  
Boron Diffusion ◽  
Boron Doped ◽  
Chemical Etch ◽  
Etch Stop

Diffusion-induced dislocations in silicon have long been of interest in semiconducting devices. Several investigations concerning the dislocations induced by doping of Si were carried out during the early sixties. However, there are still a number of unresolved questions concerning this problem. Because the boron doped chemical etch-stop technique is widely used in the fabrication of microsensors, new interest has arisen in the role of dislocations induced by boron diffusion and the behavior of these dislocations on the mechanical properties of microsensors. The doping of Si in this technique is heavy (>5x1019cm-3) and, consequently, the density of induced dislocations in the wafer is large. The dislocations will probably then play a critical role on the mechanical properties of thin Si wafers used in the etch-stop technique.

Hydraulic Fracturing Design Developments Towards Improved Effectiveness in North Kuwait Reservoirs

2021 ◽  
Author(s):  
Zamzam Mohammed Ahmed ◽  
Abrar Mohammed Alostad ◽  
Liu Pei Wu
Keyword(s):  
Hydraulic Fracturing ◽  
High Stress ◽  
Natural Fracture ◽  
Unconventional Reservoirs ◽  
Fiscal Year ◽  
Reservoir Pressure ◽  
Gas Field ◽  
Matrix Acidizing ◽  
Field Development

Abstract The North Kuwait Jurassic Gas (NKJG) reservoirs pose productivity challenges due to their geological heterogeneity, complex tectonic settings, high stress anisotropy, high pore pressure, and high bottom-hole temperature. Additionally, high natural fracture intensity in clustered areas play an important role in the wells hydrocarbon deliverability. These challenges are significant in field development starting from well design and stimulation up to production stages. The Gas Field Development Group (GFDG) are introducing for the first time in Kuwait new completion designs at high fracturing intensity; open-hole Multi Stage Completions (MSC), 4.5" Monobores and hybrid completions along with customized and efficient stimulation methods. This development strategy designed to overcome reservoir difficulties and enhance the well performance during initial testing and long-term production phases. At early stages of production, most of the wells were stimulated with simple matrix acidizing jobs and this method was sufficient to reach commercial production in conventional reservoirs. However, the reservoir depletion trend has negatively affected stimulation effectiveness and the wells performance in the recent years; hence, short and long-term solutions introduced to manage the sub-hydrostatic reservoir pressure. Our current focus is on the short-term stimulation solutions as they are relatively easier to apply compared to the long-term solutions that require additional resources, which are not available in the country. As a result, the stimulation methods, specifically the hydraulic fracturing treatments, increased production dramatically compared to previous years and it applied across North Kuwait Fields in conventional and unconventional reservoirs to reach the production targets of 2020-2021. The hydraulic fracturing treatment designs improved during the 2020-2021 fiscal year. The number of operations tripled compared to before and alternative chemical treatments with new fracturing designs implemented. In addition, these treatments executed across different well completions and reservoir properties. The objectives behind each fracturing treatment were different; for example: discovering new areas, re-stimulating under-performing wells, fracturing unconventional reservoirs, etc. Some promising wells did not flow as per expectation after matrix acidizing treatments despite the logs showing good reservoir quality similar to offset wells with good production. After re-stimulating with acid fracturing, the wells performed much better and one of them set a benchmark as the best producer amongst the offset wells. This paper evaluates the gaps in developing NKJG reservoirs, including fracturing treatments and highlights of the pros/cons for each operation, which in future supports the improvement of stimulation job designs. Moreover, it reveals the future requirements that control the operation success and how to reduce the well cleaning time post-fracturing in the event of low reservoir pressure. Finally, it describes how the outcome of the analyses directly assists reaching the production targets; since NKJG's production mainly depends on stimulation techniques.

scholarly journals The Propagation Behavior of Hydraulic Fracture in Rock Mass with Cemented Joints

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Yongxiang Zheng ◽  
Jianjun Liu ◽  
Yun Lei
Keyword(s):  
Hydraulic Fracturing ◽  
Univariate Analysis ◽  
Fracture Propagation ◽  
Fracture Network ◽  
Parameter Analysis ◽  
Natural Fracture ◽  
Hydraulic Fractures ◽  
Fracture Networks ◽  
Form Complex ◽  
Propagation Behavior

The formation of the fracture network in shale hydraulic fracturing is the key to the successful development of shale gas. In order to analyze the mechanism of hydraulic fracturing fracture propagation in cemented fractured formations, a numerical simulation about fracture behavior in cemented joints was conducted based firstly on the block discrete element. And the critical pressure of three fracture propagation modes under the intersection of hydraulic fracturing fracture and closed natural fracture is derived, and the parameter analysis is carried out by univariate analysis and the response surface method (RSM). The results show that at a low intersecting angle, hydraulic fractures will turn and move forward at the same time, forming intersecting fractures. At medium angles, the cracks only turn. At high angles, the crack will expand directly forward without turning. In conclusion, low-angle intersecting fractures are more likely to form complex fracture networks, followed by medium-angle intersecting fractures, and high-angle intersecting fractures have more difficulty in forming fracture networks. The research results have important theoretical guiding significance for the hydraulic fracturing design.

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