Yingfeng Meng

Estimation of Wellbore and Formation Temperatures during the Drilling Process under Lost Circulation Conditions

Significant change of wellbore and surrounding formation temperatures during the whole drilling process for oil and gas resources often leads by annulus fluid fluxes into formation and may pose a threat to operational security of drilling and completion process. Based on energy exchange mechanisms of wellbore and formation systems during circulation and shut-in stages under lost circulation conditions, a set of partial differential equations were developed to account for the transient heat exchange process between wellbore and formation. A finite difference method was used to solve the transient heat transfer models, which enables the wellbore and formation temperature profiles to be accurately predicted. Moreover, heat exchange generated by heat convection due to circulation losses to the rock surrounding a well was also considered in the mathematical model. The results indicated that the lost circulation zone and the casing programme had significant effects on the temperature distributions of wellbore and formation. The disturbance distance of formation temperature was influenced by circulation and shut-in stages. A comparative perfection theoretical basis for temperature distribution of wellbore-formation system in a deep well drilling was developed in presence of lost circulation.

Propagation of Measurement-While-Drilling Mud Pulse during High Temperature Deep Well Drilling Operations

Signal attenuates while Measurement-While-Drilling (MWD) mud pulse is transmited in drill string during high temperature deep well drilling. In this work, an analytical model for the propagation of mud pulse was presented. The model consists of continuity, momentum, and state equations with analytical solutions based on the linear perturbation analysis. The model can predict the wave speed and attenuation coefficient of mud pulse. The calculated results were compared with the experimental data showing a good agreement. Effects of the angular frequency, static velocity, mud viscosity, and mud density behavior on speed and attenuation coefficients were included in this paper. Simulated results indicate that the effects of angular frequency, static velocity, and mud viscosity are important, and lower frequency, viscosity, and static velocity benefit the transmission of mud pulse. Influenced by density behavior, the speed and attenuation coefficients in drill string are seen to have different values with respect to well depth. For different circulation times, the profiles of speed and attenuation coefficients behave distinctly different especially in lower section. In general, the effects of variables above on speed are seen to be small in comparison.

An Anisotropic Strength Model for Layered Rocks Considering Planes of Weakness

List of Symbols b Inclination angle between planes of weakness and the major principal stress VR Volume of layered rock Vm Volume of matrix Vf Volume of weakness planes cR b ð Þ, /R b ð Þ Cohesion and internal friction angle of layered rock at angle b cm, /m Cohesion and friction angle of matrix cf , /f Cohesion and friction angle of weakness plane lR b ð Þ Friction coefficient (tan/R) of layered rock at angle b rf b ð Þ Strength reduction coefficient of anisotropic planes at angle b rc b ð Þ Uniaxial compressive strength of layered rock at angle b q Inclination angle of minimum shear strength c, d Inclination angle of minimum cohesion and friction angle Rc Degree of anisotropy a, b, c1,2, /1,2, b’s, d’s, ĉ, l̂ Constants

Cuttings Transport Models and Experimental Visualization of Underbalanced Horizontal Drilling

Aerated underbalanced horizontal drilling technology has become the focus of the drilling industry at home and abroad, and one of the engineering core issues is the horizontal borehole cleaning. Therefore, calculating the minimum injection volume of gas and liquid accurately is essential for the construction in aerated underbalanced horizontal drilling. This paper establishes a physical model of carrying cuttings and borehole cleaning in wellbore of horizontal well and a critical transport mathematical model according to gas-liquid-solid flow mechanism and large plane dunes particle transport theory.

Modified Hoek–Brown failure criterion for anisotropic rocks

The direction-dependent strength behavior of anisotropic rocks is a common characteristic. It is essential to develop the model that can describe the nonlinearity as well as the anisotropy in the triaxial strength behavior of the rocks. In the present study, a modified Hoek–Brown failure criterion was developed to describe the triaxial strength behavior of the rocks by the using of anisotropic index (

CUTTINGS-CARRIED THEORY AND EROSION RULE IN GAS DRILLING HORIZONTAL WELL

\alpha_{\beta }

Wellbore Flow Rules in Marine Natural Gas Hydrate Reservoir Drilling

αβ). The procedures for determining the failure criterion parameters are introduced. In the model, the estimation of the uniaxial compressive strength at a given angle β was required, so an empirical equation for predicting the variation of the uniaxial compressive strength of anisotropic rocks is presented. The performance of the proposed equation was tested by using a triaxial test database compiled by Singh (Rock Mech Rock Eng 48(4):1387–1405, 2015). The variation of the uniaxial compressive strength was then incorporated into the modified Hoek–Brown failure criterion. Based on the analysis of the extensive triaxial test database, it was possible to accurately predict the strength of anisotropic rocks using limited test data. It is concluded that the modified Hoek–Brown failure criterion has good ability in predicting the strength of anisotropic rocks.

Analysis of Decomposition for Structure I Methane Hydrate by Molecular Dynamics Simulation

In this work, a methodology for characterizing reservoir pore pressure and permeability during underbalanced drilling of horizontal wells was presented. The methodology utilizes a transient multiphase wellbore flow model that is extended with a transient well influx analytical model during underbalanced drilling of horizontal wells. The effects of the density behavior of drilling fluid and wellbore heat transfer are considered in our wellbore flow model. Based on Kneissl’s methodology, an improved method with a different testing procedure was used to estimate the reservoir pore pressure by introducing fluctuations in the bottom hole pressure. To acquire timely basic data for reservoir characterization, a dedicated fully automated control real-time data monitoring system was established. The methodology is applied to a realistic case, and the results indicate that the estimated reservoir pore pressure and permeability fit well to the truth values from well test after drilling. The results also show that the real-time data monitoring system is operational and can provide accurate and complete data set in real time for reservoir characterization. The methodology can handle reservoir characterization during underbalanced drilling of horizontal wells.