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Abstract This paper introduces a method to fracture more than 30 zones in a single well per day and also how to fracture low permeability zones when the impermeable barrier(s) to high permeability and high water cut zones are only about 0.5 m thick and not create channels in the cement sheathe. The above methods are used in a large scale in Daqing Oil Field (about 1,000 wells per year since 1980). The results are quite good, cumulative incremental oil production by these fracturing methods is about 60 million tons; the fracturing costs per ton of incremental oil is about $ 6. Introduction Daqing Oil Field is a multi-zone heterogeneous reservoir. A well drilled vertically downwards encounters on the average about 150 to 200 pay zones in an interval of about 200 m. (Figure 1), which means the average pay zone and impermeable zone each are only 0.5 to 0.7 m. The thickness of the pay zones varies from 0.2 m to 15 m; the permeability varies from 10 md to 1,500 md. The injection and production rate of high permeability zones is very high and very low for low permeability zones. If all the low permeability zones could be fractured to increase their injectivity and productivity, then a more uniform flood front and production rate between high and low permeability zones could be obtained and thus higher recovery. However, in Daqing, on the average 30 low permeability zones in a well need to be fractured. With commonly used methods, only a few zones could be fractured in one day, to fracture 30 zones would need a large amount of service work and a long period of time, which would in turn greatly increase the cost. With many impermeable barriers being very thin, to prevent channeling, many zones that need to cannot be fractured. To solve the above questions, 3 techniques were modified and combined into a new technique. These 3 techniques are: multiple-zone fracturing using packers, limited-entry fracturing and pressure-balanced fracturing. These techniques and how they are integrated into one and the field results are explained in this paper. Important Aspects of the Technique Multiple-Zone Fracturing Multiple-zone fracturing technique has been used in Daqing since the early 1970s. Multiple (3 to 4) inflatable packers and multiple selective opened mandrels are run in tandem in the well (Figure 2) opposite the zones that need to be fractured. The first mandrel and first 2 packers (from bottom up) are open (or can be inflated) when run in the well and on start of the fracturing job. The zone opposite the mandrel between the upper and lower packer is first fractured. Then a ball is dropped in to trip open the second mandrel, block the lower mandrel and open the 3rd packer. On immediately re-starting the fracturing job, the second zone is fractured, and so on until 3 or 4 zones are fractured. Between fracturing jobs, the tubing string is not pulled or set down, only a tripping ball is dropped down, greatly shortening the waiting time between fracturing jobs. The packers are inflatable ones, after the fracturing job, they automatically retract to their original outer diameter. Sometimes there is sand settled on top of the packers that prevent pulling the tubing string. To avoid this problem, all the mandrels are joined directly on top of the lower packer, when fracturing, the high volume and velocity of the fracturing fluid will form strong turbulence, which will carry away most of the fracturing sand (proppant), little will settle down on top of the packer. These measures and features (inflatable packers, turbulent flow and direct joining of the mandrel to the lower packer) make it relatively easy to pull the tubing string out of the well after fracturing. This type of fracturing has been performed 2,000 to 2,500 times per year in Daqing for 30 years, which shows that it is quite a reliable technique.
- Asia > China > Heilongjiang > Songliao Basin > Daqing Field > Yian Formation (0.99)
- Asia > China > Heilongjiang > Songliao Basin > Daqing Field > Mingshui Formation (0.99)
Abstract In the last five years North America has changed the oil and gas markets by using horizontal drilling and multistage hydraulic fracturing to unlock the hydrocarbons in lowโpermeability reservoirs. This unexpected increase in natural gas production over a short period of time in the US has led to extremely low prices due to overโsupplying the market. There are indications that the US will become an exporter of natural gas, rather than an importer, as originally planned. These plays require new technologies that enable reservoir characterization, horizontal drilling, multistage completions, and multistage hydraulic fracturing. All these technologies have evolved at a very rapid pace and continue to do so. This paper will focus on the completion technologies. Three completion techniques have emerged as the most effective and efficient in these types of formations; plugโandโperf, ballโactivated completions, and coiled tubingโactivated completions. The plugโandโperf technique is cemented in place and uses composite bridge plugs and perforations to isolate and divert the fracture to the correct stage. Ballโactivated completions use openhole packers to isolate the annulus and ballโactivated fracture (frac) sleeves to divert the fracture to the intended stage. Coiled tubingโactivated completions use cement to isolate the annulus, and coiled tubingโactivated sleeves or perforations to divert the frac fluid. Each completion technique has benefits and considerations. The primary purpose of this paper is to give an overview of these completion types, discuss the benefits and considerations, and how they compare in different applications from an operations point of view. The secondary purpose of this paper is to discuss how drilling, completion, and fracturing can greatly affect each other and create limitations if these processes do not collaborate.
Summary Field and experimental data have shown that perforation erosion during shale gas stimulation invalidates the assumption of a constant coefficient of discharge. However, perforation erosion is not fully understood yet. In this work, a perforation erosion model was built using computational fluid dynamics (CFD) and validated against laboratory data. We then conducted parametric studies to investigate the impact of treatment rate, proppant concentration, proppant size, and fluid viscosity on perforation erosion. Our results demonstrated that a higher treatment rate and larger proppant lead to higher erosion to the perforation diameter. Perforation erosion decreased when fluid viscosities increased from 10 to 100 cp, and then increased when the fluid viscosity was increased to 1,000 cp. Our new understandings could be applied to improve perforation design in shale wells.
- Geology > Geological Subdiscipline > Geomechanics (0.96)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.45)
Summary Field and experimental data have shown that perforation erosion during shale gas stimulation invalidates the assumption of a constant coefficient of discharge. However, perforation erosion is not fully understood yet. In this work, a perforation erosion model was built using computational fluid dynamics (CFD) and validated against laboratory data. We then conducted parametric studies to investigate the impact of treatment rate, proppant concentration, proppant size, and fluid viscosity on perforation erosion. Our results demonstrated that a higher treatment rate and larger proppant lead to higher erosion to the perforation diameter. Perforation erosion decreased when fluid viscosities increased from 10 to 100 cp, and then increased when the fluid viscosity was increased to 1,000 cp. Our new understandings could be applied to improve perforation design in shale wells.
- Geology > Geological Subdiscipline > Geomechanics (0.96)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.45)
Study of Proppant Erosion in Multistage Hydraulic Fracturing Using Computational Fluid Dynamics Modeling
Yuan, Peng (Baker Hughes Incorporated) | Zhang, Hao (Baker Hughes Incorporated) | Huang, Xu (Baker Hughes Incorporated) | Han, Jiahang (Baker Hughes Incorporated) | Zhou, Quming (Baker Hughes Incorporated) | Mezzatesta, Alberto (Baker Hughes Incorporated) | Bao, Jie (Pacific Northwest National Laboratory)
Abstract Multistage hydraulic fracturing is widely applied for developing unconventional reservoirs with low permeability. The plug-and-perf method is the most commonly used staging method especially for horizontal wells. Fracturing fluids are usually pumped from the surface to create fractures after perforation clusters are established for each stage; next, proppants are placed into the fractures to keep them open. Field and experimental work have shown that proppant transport in multistage plug-and-perf completions can cause severe erosion on perforations. However, modeling proppant erosion process is still an intricate task that proves to be challenging within the industry due to complexity of the problem. In this work, proppant erosion is investigated by using computational fluid dynamics (CFD) modeling. The effects of sand particle diameter, proppant loading, fracturing fluids viscosity, slurry injection rates, and the pipe angle are analyzed to determine the rate of erosion within the perforations. Several erosion models are used and the simulation results are compared. The numerical simulation results produced by using the proposed CFD model indicate that proppant can increase the diameter of the perforation. The unevenness of diameter increasing would further compromise the fracturing design because of one cluster accepting more fluid than its counterparts and affecting the distribution of the proppants in the cluster. The flow lines and couplings also show significant wear due to proppant erosion. The simulation results using the Oak erosion model are found to agree with the findings in the inside-casing experimental test. The results of this study indicate that proppant erosion in multistage hydraulic fracturing can be accurately modelled when proppant properties, fracture geometry, and slurry rheology are all considered in the CFD simulation model. The simulation methodology proposed and discussed in this paper provides a better understanding of fluid and proppant behavior and proves that CFD is an effective tool for reducing the wear of perforations and pipes caused by proppant erosion and hence, optimizing hydraulic fracturing design.