scholarly journals Study on Method of Determining the Safe Operation Window of Drilling Fluid Density with Credibility in Deep Igneous Rock Strata

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Chao Han ◽  
Zhichuan Guan ◽  
Chuanbin Xu ◽  
Fuhui Lai ◽  
Pengfei Li
Keyword(s):  
Igneous Rock ◽  
Drilling Fluid ◽  
Prediction Method ◽  
Large Error ◽  
Fluid Density ◽  
Safe Operation ◽  
Collapse Pressure ◽  
Modified Method ◽  
Fracture Pressure ◽  
Rock Strata

It is difficult to determine the safe operation window of drilling fluid density (SOWDFD) for deep igneous rock strata. Although the formation three-pressure (pore pressure, collapse pressure, and fracture pressure) prediction method with credibility improves the accuracy of formation three-pressure prediction, it still has a large error for deep igneous strata. To solve this problem, a modified method of the SOWDFD in deep igneous rock strata is proposed based on the leakage statistics of adjacent wells. This method is based on the establishment of the SOWDFD with credibility. Through statistical analysis of drilling fluid density of igneous rock leaky formation group in adjacent wells, the fracture leakage law of the formation is revealed and the upper limit of leak-off pressure containing probability information is obtained. Finally, the modified SOWDFD with credibility for deep igneous rock strata is formed. In this work, the proposed method was used to compute the SOWDFD with credibility of SHB well in Xinjiang, China. Results show that the modified density window is consistent with the field drilling conditions and can reflect the narrow density window in the Permian and lower igneous strata. Combined with the formation three-pressure prediction method with credibility and the actual leakage law of adjacent wells, it can effectively improve the prediction accuracy of the SOWDFD for deep igneous rock strata. The findings of the study can help in better understanding of the complex downhole geological environment in deep igneous rock strata and making reasonable drilling design scheme.

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.

Leak-Off Pressure Prediction with the Integration of Fully Coupled 3D DFN Modeling in Fractured Reservoir

2021 ◽  
Author(s):  
Dan Xie ◽  
Wei Zhou ◽  
Sinan Cheng ◽  
Gang Tian ◽  
Sheng Zheng ◽  
...  
Keyword(s):  
Rational Design ◽  
Drilling Fluid ◽  
Prediction Method ◽  
Junggar Basin ◽  
Natural Fracture ◽  
Pressure Curve ◽  
Fractured Reservoir ◽  
Lost Circulation ◽  
Fracture Pressure ◽  
Fully Coupled

Abstract Leak-off pressure is a main factor to induce formation leak-off so that it can be utilized as a crucial parameter to analyze the causation of well leak-off accidents, and that in-depth investigation on leak-off pressure is of vital importance for secure drilling. By analyzing the characteristics of leak-off formation, this paper divides the leak-off into natural leak-off and fractured leak-off, and then defines the conception of minimal leak-off pressure. The leak-off mechanism of fractured formation is investigated. Investigation results show that the currently existent prediction method of fracture pressure is established on the foundations of non-filtration borehole wall assumption as well as the Terzaghi effective stress model. These foundations are not consistent with the practical features of thief formation, which would inevitably cause deviation of calculated results with actualization. Natural leak-off formation constitutes the majority of formation leak-off phenomena. Therefore, it is urgent to build up the leak-off pressure curve instead of fractured pressure curve and take precautions against natural leak-off. The technique of leak-off pressure prediction with fully-coupled 3D natural fracture modeling was applied in the fractured reservoir which located in the northwest of Junggar Basin, China. Case analyses have proved that this lost circulation pressure model is of sufficiency in scientific bases and pertinence. The prediction result derived from the model is relatively consistent with the actual situation and consequently provides a substantial basis for a rational design of the drilling fluid density as well as the leak resistance and sealing. Therefore it is suggested that the design of drilling engineering should take the lost circulation pressure into consideration.

A Novel Method to Determine the Drilling Fluid Density for Gypsum-Salt Layer

2021 ◽  
Author(s):  
Jitong Liu ◽  
Wanjun Li ◽  
Haiqiu Zhou ◽  
Yixin Gu ◽  
Fuhua Jiang ◽  
...  
Keyword(s):  
Drilling Fluid ◽  
In Situ Stress ◽  
Wellbore Stability ◽  
Shrinkage Rate ◽  
Fluid Density ◽  
Salt Layer ◽  
Rock Creep ◽  
Key Factor ◽  
Well Abandonment

Abstract The reservoir underneath the salt bed usually has high formation pressure and large production rate. However, downhole complexities such as wellbore shrinkage, stuck pipe, casing deformation and brine crystallization prone to occur in the drilling and completion of the salt bed. The drilling safety is affected and may lead to the failure of drilling to the target reservoir. The drilling fluid density is the key factor to maintain the salt bed’s wellbore stability. The in-situ stress of the composite salt bed (gypsum-salt -gypsum-salt-gypsum) is usually uneven distributed. Creep deformation and wellbore shrinkage affect each other within layers. The wellbore stability is difficult to maintain. Limited theorical reference existed for drilling fluid density selection to mitigate the borehole shrinkage in the composite gypsum-salt layers. This paper established a composite gypsum-salt model based on the rock mechanism and experiments, and a safe-drilling density selection layout is formed to solve the borehole shrinkage problem. This study provides fundamental basis for drilling fluid density selection for gypsum-salt layers. The experiment results show that, with the same drilling fluid density, the borehole shrinkage rate of the minimum horizontal in-situ stress azimuth is higher than that of the maximum horizontal in-situ stress azimuth. However, the borehole shrinkage rate of the gypsum layer is higher than salt layer. The hydration expansion of the gypsum is the dominant reason for the shrinkage of the composite salt-gypsum layer. In order to mitigate the borehole diameter reduction, the drilling fluid density is determined that can lower the creep rate less than 0.001, as a result, the borehole shrinkage of salt-gypsum layer is slowed. At the same time, it is necessary to improve the salinity, filter loss and plugging ability of the drilling fluid to inhibit the creep of the soft shale formation. The research results provide technical support for the safe drilling of composite salt-gypsum layers. This achievement has been applied to 135 wells in the Amu Darya, which completely solved the of wellbore shrinkage problem caused by salt rock creep. Complexities such as stuck string and well abandonment due to high-pressure brine crystallization are eliminated. The drilling cycle is shortened by 21% and the drilling costs is reduced by 15%.

Density and Drag Reduction With Hollow Glass Additives

2014 ◽  
Author(s):  
Bahri Kutlu ◽  
Evren M. Ozbayoglu ◽  
Stefan Z. Miska ◽  
Nicholas Takach ◽  
Mengjiao Yu ◽  
...  
Keyword(s):  
Drag Reduction ◽  
Rheological Behavior ◽  
Drilling Fluid ◽  
Hydraulic Drag ◽  
Effect Of Temperature ◽  
Survival Ratio ◽  
Fluid Density ◽  
Hollow Glass ◽  
Glass Spheres ◽  
Reduction Effect

This study concentrates on the use of materials known as hollow glass spheres, also known as glass bubbles, to reduce the drilling fluid density below the base fluid density without introducing a compressible phase to the wellbore. Four types of lightweight glass spheres with different physical properties were tested for their impact on rheological behavior, density reduction effect, survival ratio at elevated pressures and hydraulic drag reduction effect when mixed with water based fluids. A Fann75 HPHT viscometer and a flow loop were used for the experiments. Results show that glass spheres successfully reduce the density of the base drilling fluid while maintaining an average of 0.93 survival ratio, the rheological behavior of the tested fluids at elevated concentrations of glass bubbles is similar to the rheological behavior of conventional drilling fluids and hydraulic drag reduction is present up to certain concentrations. All results were integrated into hydraulics calculations for a wellbore scenario that accounts for the effect of temperature and pressure on rheological properties, as well as the effect of glass bubble concentration on mud temperature distribution along the wellbore. The effect of drag reduction was also considered in the calculations.

scholarly journals Laboratory Study on Core Fracturing Simulations for Wellbore Strengthening

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-18 ◽  
Author(s):  
Biao Ma ◽  
Xiaolin Pu ◽  
Zhengguo Zhao ◽  
Hao Wang ◽  
Wenxin Dong
Keyword(s):  
Bearing Capacity ◽  
Laboratory Study ◽  
Drilling Fluid ◽  
Drilling Fluids ◽  
Lost Circulation ◽  
The Core ◽  
Fracture Pressure ◽  
Fluid Systems ◽  
Fracturing Process ◽  
Wellbore Strengthening

The lost circulation in a formation is one of the most complicated problems that have existed in drilling engineering for a long time. The key to solving the loss of drilling fluid circulation is to improve the pressure-bearing capacity of the formation. The tendency is to improve the formation pressure-bearing capacity with drilling fluid technology for strengthening the wellbore, either to the low fracture pressure of the formation or to that of the naturally fractured formation. Therefore, a laboratory study focused on core fracturing simulations for the strengthening of wellbores was conducted with self-developed fracture experiment equipment. Experiments were performed to determine the effect of the gradation of plugging materials, kinds of plugging materials, and drilling fluid systems. The results showed that fracture pressure in the presence of drilling fluid was significantly higher than that in the presence of water. The kinds and gradation of drilling fluids had obvious effects on the core fracturing process. In addition, different drilling fluid systems had different effects on the core fracture process. In the same case, the core fracture pressure in the presence of oil-based drilling fluid was less than that in the presence of water-based drilling fluid.

Research on depth prediction method of igneous rock underlying strata

2021 ◽  
Author(s):  
Jiyan Cai ◽  
Junting Song ◽  
Tao Tian ◽  
Min Gong
Keyword(s):  
Igneous Rock ◽  
Prediction Method ◽  
Depth Prediction

Effect of Drilling Fluid Temperature on Formation Fracture Pressure Gradient

2021 ◽  
Author(s):  
Ahmed Mostafa Samak ◽  
Abdelalim Hashem Elsayed
Keyword(s):  
High Temperature ◽  
Pressure Gradient ◽  
Thermal Effect ◽  
Drilling Fluid ◽  
Wellbore Stability ◽  
Cooling Effect ◽  
Fluid Temperature ◽  
Lost Circulation ◽  
Fracture Pressure ◽  
Downhole Temperature

Abstract During drilling oil, gas, or geothermal wells, the temperature difference between the formation and the drilling fluid will cause a temperature change around the borehole, which will influence the wellbore stresses. This effect on the stresses tends to cause wellbore instability in high temperature formations, which may lead to some problems such as formation break down, loss of circulation, and untrue kick. In this research, a numerical model is presented to simulate downhole temperature changes during circulation then simulate its effect on fracture pressure gradient based on thermo-poro-elasticity theory. This paper also describes an incident occurred during drilling a well in Gulf of Suez and the observations made during this incident. It also gives an analysis of these observations which led to a reasonable explanation of the cause of this incident. This paper shows that the fracture pressure decreases as the temperature of wellbore decreases, and vice versa. The research results could help in determining the suitable drilling fluid density in high-temperature wells. It also could help in understanding loss and gain phenomena in HT wells which may happen due to thermal effect. The thermal effect should be taken into consideration while preparing wellbore stability studies and choosing mud weight of deep wells, HPHT wells, deep water wells, or wells with depleted zones at high depths because cooling effect reduces the wellbore stresses and effective FG. Understanding and controlling cooling effect could help in controlling the reduction in effective FG and so avoid lost circulation and additional unnecessary casing points.

Application of drilling fluid density detection based on intelligent sensor

2008 ◽  
Author(s):  
Hong He ◽  
Hengtian Jia ◽  
Hongyan Pan ◽  
Shenglei Han ◽  
Xin Cui
Keyword(s):  
Drilling Fluid ◽  
Fluid Density ◽  
Intelligent Sensor
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