海洋钻机三维设计数据库与模型规划研究

随着数字化技术和数字孪生技术的不断应用和工程全命周期管理理念的不断完善,海洋钻机的各类数据信息系统也在不断地开发。为了解除三维设计数据库和模型规对数字化成果和应用范围的限制,本文对海洋钻机三维设计数据库与模型规划开展了深入的研究,并得出相关规划研究成果。     

多组分烃类混合物气液两相流格子玻尔兹曼模型

针对传统格子玻尔兹曼模型无法处理真实多组分混合物气液两相流的问题,提出了一种新的基于四参数(临界温度、临界压力、偏心因子、体积修正因子)状态方程的多组分格子玻尔兹曼模型。模型首先使用烃类混合物状态方程计算混合流体间作用力,并提出一种将混合流体作用力分配给各流体组分的方法,从而计算出混合流体中各组分所受作用力,再使用精确差分方法将组分作用力引入格子玻尔兹曼模型。同时为正确反应黏度变化对多相体系流动过程的影响,引入LBC(Lorentz-Bray-Clark)黏度模型计算混合流体的黏度。利用该模型,分别模拟了甲烷、乙烷、丙烷等多组分气液两相共存问题。新模型计算结果与使用逸度平衡方法获得的理论解吻合度较高,验证了新模型的正确性。图7表1参24     

A compressional wave seismic model for the Ashrafi-1 well

Despite disappointing drilling results, the South Caspian basin has yielded scientific results of significant value to future exploration. This paper describes work that utilized data from the offshore Ashrafi-1 well, but we believe it has applications to exploration elsewhere in Azerbaijan. The North Absheron Operating Company (NAOC) drilled the Ashrafi-1 well between November 30, 1997 and February 6, 1998 to a total depth of 3668 m (sub Caspian sea level). The Balakhany and Pereryva Suite (SP) Formations were wet but the Upper Kirmaku Sandy (NKP) Formation tested oil and the Lower Kirmaku (PK) Formation tested gas, both at high flow rates. Anomalously high stack amplitude responses, generally conforming to structural closure, had been observed in the 3D seismic data at the NKP and PK Formations prior to drilling of the well. An offset synthetic modeling study was undertaken, post-drill, to determine the in-situ amplitude response (stack and amplitude variation with offset, or AVO) for both pay and wet zones and to model the changes in AVO and stacked amplitudes in response to changes in variables such as thickness, fluid fill and porosity. As well as the 3D seismic data set, the principal data sources used were a dipole sonic log for compressional wave velocity (Vp) and shear wave velocity (Vs); checkshots for time-to depth (T–D) conversion; a density log; log interpretations of porosity; fluid properties based on pressure–volume–temperature (PVT) analysis of fluids from drill stem tests (DSTs) and pressure/temperature data. In this simple case, despite the highly permeable reservoir rocks, the Gassmann assumption of immobile fluids within the pore space was used. Although the effects of partial gas saturation are known to be a problem elsewhere in this basin, density modeling derived from borehole-guided long offset AVO was not attempted. Despite this, normal incident amplitudes, derived from pre-stack data, cross-plotted against amplitude gradients suggest a methodology for distinguishing wet sandstones from gas and oil in this basin in the absence of recent leakage. Despite the difference in response for oil and gas (oil gave a stronger response than gas), a statistically meaningful number of wells is not yet available and this result may be influenced by local lithologic effects. Thus, the ability to distinguish oil from gas ahead of the drill bit — which is of vital importance in evaluating commerciality — is not proven.     

A computational fluid dynamic model for evaluating the performance of crude oil gasification

Gasification is a clean technology which converts the liquid or solid fuels into a high caloric value syngas for power generation. In this research work, we developed a computational fluid dynamic model of crude oil gasification for hydrogen production; the accuracy of the model was approved in our previous work. Effects of some important factors such as residence time, steam/fuel ratio and equivalence ratio on hydrogen yield, and char conversion were explored. Results showed that the residence time and steam/fuel ratio play a major role in the process. It was also found that the equivalence ratio has a negative effect on the hydrogen yield and a positive effect on the char conversion.     

A New Approach for Predrilling the Unconfined Rock Compressive Strength Prediction

Abstract

A reasonable knowledge of rock's physical and mechanical properties could save the cost of drilling and production of a reservoir to a large extent by selection of proper operating parameters. In addition, a master development plan (MDP) for each oilfield may contain many enhanced oil recovery procedures that take advantage of rock mechanical data and principles. Thus, an integrated rock mechanical study can be considered an investment in field development.

The unconfined compressive strength (UCS) of rocks is the important rock mechanical parameter and plays a crucial role when drilling an oil or gas well. A drilling operation is an interaction between the rock and the bit and the rock will fail when the resultant stress is greater than the rock strength. UCS is actually the stress level at which rock is broken down when it is under a uniaxial stress. It can be used for bit selection, real-time wellbore stability analysis, estimation an optimized time for pulling up the bit, design of enhanced oil recovery (EOR) procedures, and reservoir subsidence studies.

Rock strength can be estimated along a drilled wellbore using different approaches, including laboratory tests, core–log relationships, and penetration model approaches. Although this rock strength profile can be used for future investigation of formations around the wellbore, they are actually dead information. Dead rock strength data may not be useful for designing a well in a blind location (infill drilling). Rock strength should be predicted prior to drilling operations. These sort of data are helpful in proposing a drilling program for a new well.

In this research, new equations for estimation of rock strength in Ahwaz oilfield are formulated based on statistical analysis. Then, they are utilized for estimation of the rock strength profile of 36 wells in a Middle Eastern oilfield. An artificial neural network is then utilized for prediction of UCS in any predefined well trajectory. Cross-validation tests showed that the results of the network were compatible with reality. This approach has proven to be useful for estimation of any designed well trajectory prior to drilling.     

A model for the flow of gas mixtures in adsorption dominated dual-porosity reservoirs incorporating multi-component matrix diffusion—Part II numerical algorithm and application examples

In part one of this study a matrix-fracture transfer function was presented for multi-species gas migration in dual-porosity media. This second part presents the numerical implementation of this transfer function. Since the transfer function proposed in Part I is of an integral form with history-dependency and the resultant flow equations become a set of integro-(partial) differential equations, an algorithm is developed here for these equations. The algorithm is formulated using a step-by-step finite difference procedure combined with a fully implicit quadrature scheme. The quadrature scheme is based on the modified trapezoidal method and is designed for variable time-step size. The transfer function and the algorithm developed are incorporated into the commercial gas reservoir simulator SIMED II, and three examples are illustrated here. Example 1 demonstrates the performance and feasibility of the algorithm in applications, and Example 2 discusses the effect of higher order terms as well as its influence on flow profiles. The impact of mutual-diffusivity to flow profiles and well performance is illustrated in Example 3.