Borehole Stability Logging Analysis in Zhenjing Oilfield, Ordos Basin, China

2013 ◽  
Vol 344 ◽  
pp. 8-14
Author(s):  
Li Min Ran ◽  
He Ping Pan ◽  
Gong Qiang Li ◽  
Yong Gang Zhao
Keyword(s):  
Oil And Gas ◽  
Ordos Basin ◽  
Maximum Tensile Stress ◽  
Practical Significance ◽  
Borehole Stability ◽  
Collapse Pressure ◽  
Stress Theory ◽  
Gas Drilling ◽  
Fracture Pressure ◽  
Column Pressure

There is very important practical significance for borehole stability to oil and gas drilling and production. When the mud density is too large (mud column pressure too high),the formation will be fractured. When the the mud density is too low (mud column pressure too low), the borehole wall will be collapsed, and hole will be enlarged. In this paper, the fracture pressures of the formations were determined by using the maximum tensile stress theory. The formation collapse pressures were determined by using the Coulomb - Moore intensity criteria. According to the fracture pressure and collapse pressure to evaluate the borehole stability. The two wells stability evaluation examples were given, and the borehole security mud window were calculated.

Study on Borehole Stability of Unconsolidated Sandstone in Depleted Reservior

2012 ◽  
Vol 616-618 ◽  
pp. 720-725
Author(s):  
Qiang Tan ◽  
Jin Gen Deng ◽  
Bao Hua Yu
Keyword(s):  
Oil And Gas ◽  
Drilling Fluid ◽  
Wellbore Stability ◽  
Formation Pressure ◽  
Borehole Stability ◽  
Oil And Gas Development ◽  
Collapse Pressure ◽  
Lost Circulation ◽  
Fracture Pressure ◽  
Pressure Depletion

Reservoir pressure will decline generally along with production in the oil and gas development process. There are some problems such as borehole collapse or reduced diameter and lost circulation in drilling of initial production stage in unconsolidated sandstone. As the formation pressure declines the stress around borehole changes, and then collapse pressure and fracture pressure are affected. Especially in directional wells, variation of wellbore stability is more complex with different borehole deviation and azimuth. The calculation models of collapse and fracture pressure in depleted reservoirs were established, and relevant data in unconsolidated sand reservoir of an oilfield in Bohai Sea was used to calculate collapse pressure and fracture pressure of directional wells in the condition of pressure depletion before and after. The results showed that collapse and fracture pressure decreased as formation pressure depletion, and safe drilling fluid density window was wider when drilled to the direction of minimum horizontal principle stress. The calculation results can be reference to drilling design of adjustment wells in unconsolidated sandstones.

Study on Shale Gas Drilling Fluids Technology

2013 ◽  
Vol 868 ◽  
pp. 651-656
Author(s):  
Gang Xie ◽  
Ming Yi Deng ◽  
Jun Lin Su ◽  
Liang Chun Pu
Keyword(s):  
Shale Gas ◽  
Drilling Fluid ◽  
Blocking Agent ◽  
Drilling Fluids ◽  
Collapse Pressure ◽  
Gas Drilling ◽  
Advantages And Disadvantages ◽  
Water Based ◽  
Column Pressure ◽  
Shale Gas Drilling

Via discussing the advantages and disadvantages of different types of oil-based drilling fluids, the main reason why oil-based drilling fluids are less used in our country is obtained that dont form a complete series of matching technology. The essence of wellbore instability caused by using water-based drilling fluids to drill shale is analyzed that the formation collapse pressure is greater than drilling fluids column pressure. The fundamental way of controlling borehole wall stability that use water-based drilling fluids to drill shale horizontal well was proposed that deeply researched the shale hydration mechanism, developed efficient blocking agent and inhibitors and established shale gas drilling fluid suppression system, which made water-based drilling fluids have excellent performance.

Geology and age of the Precambrian basement in the Windsor, Chatham, and Sarnia area, southwestern Ontario

1982 ◽  
Vol 19 (8) ◽  
pp. 1627-1634 ◽  
Author(s):  
A. Turek ◽  
R. N. Robinson
Keyword(s):  
Oil And Gas ◽  
Precambrian Basement ◽  
Grenville Province ◽  
Metasedimentary Rocks ◽  
Gas Drilling ◽  
Arch System ◽  
Grenvillian Orogeny ◽  
Anomaly Map ◽  
Paleozoic Rocks ◽  
Basement Surface

Precambrian basement in the Windsor–Chatham–Sarnia area is covered by Paleozoic rocks that are up to 1300 m thick. The basement surface is characterized by a northeast–southwest arch system with a relief of about 350 m. Extensive oil and gas drilling has penetrated and sampled this basement, and an examination of core and chip samples from 133 holes and an assessment of the magnetic anomaly map of the area have been used to produce a lithologic map of the Precambrian basement. The predominant rocks are granite gneisses and syenite gneisses but also significant are gabbros, granodiorite gneisses, and metasedimentary rocks. The average foliation dips 50° and is inferred to have a northeasterly trend. The Precambrian basement has been regarded as part of the Grenville Province. An apparent Rb–Sr whole rock isochron, for predominantly meta-igneous rocks, yields an age of 1560 ± 140 Ma. This we interpret as pre-Grenvillian, surviving the later imprint of the Grenvillian Orogeny. Points excluded from the isochron register ages of 1830, 915, and 670 Ma, and can be interpreted as geologically meaningful.

scholarly journals Fracture Initiation Model of Shale Fracturing Based on Effective Stress Theory of Porous Media

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Yuwei Li ◽  
Dan Jia
Keyword(s):  
Porous Media ◽  
Mechanical Characteristics ◽  
Oil And Gas ◽  
Elastic Anisotropy ◽  
Special Kind ◽  
Fracture Initiation ◽  
Propagation Mechanism ◽  
Stress Theory ◽  
Unconventional Oil And Gas ◽  
Initiation Pressure

Unconventional oil and gas are important resources of future energy supply, and shale gas is the focus of the development of unconventional resources. Shale is a special kind rock of porous medium, and an orderly structure of beddings aligned in the horizontal direction where causing the strong elastic anisotropy of shale is easy. A new model has been established to calculate the fracture initiation pressure with the consideration of mechanical characteristics of shale and the anisotropic tensile strength when judging rock failure. The fracture initiation model established in this paper accurately reflects the stress anisotropy and matches well with the actual situation in porous media. Through the sensitivity analysis, the results show that σv/σH, Ev/EH, υv/υH, m/s, and A/B have a certain impact on the tangential stress when the circumferential angle changes, and there is a positive relationship between the initiation pressure and the above sensitive factors except for A/B. The results can provide a valuable and effective guidance for the prediction of fracture initiation pressure and fracture propagation mechanism under special stratum conditions of shale.

Finite Element Study of the Cutting Mechanics of the Three Dimensional Rock Turning Process

2015 ◽  
Author(s):  
Demeng Che ◽  
Jacob Smith ◽  
Kornel F. Ehmann
Keyword(s):  
Finite Element ◽  
Oil And Gas ◽  
Three Dimensional ◽  
Polycrystalline Diamond ◽  
Close Correlation ◽  
Experimental Results ◽  
Failure Behavior ◽  
Fe Model ◽  
Gas Drilling ◽  
Cutting Mechanics

The unceasing improvements of polycrystalline diamond compact (PDC) cutters have pushed the limits of tool life and cutting efficiency in the oil and gas drilling industry. However, the still limited understanding of the cutting mechanics involved in rock cutting/drilling processes leads to unsatisfactory performance in the drilling of hard/abrasive rock formations. The Finite Element Method (FEM) holds the promise to advance the in-depth understanding of the interactions between rock and cutters. This paper presents a finite element (FE) model of three-dimensional face turning of rock representing one of the most frequent testing methods in the PDC cutter industry. The pressure-dependent Drucker-Prager plastic model with a plastic damage law was utilized to describe the elastic-plastic failure behavior of rock. A newly developed face turning testbed was introduced and utilized to provide experimental results for the calibration and validation of the formulated FE model. Force responses were compared between simulations and experiments. The relationship between process parameters and force responses and the mechanics of the process were discussed and a close correlation between numerical and experimental results was shown.

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