The interpretation of DST data for donghae-1 gas field, block VI-1, Korea

Donghae-1 gas field is located in Ulleung basin at offshore Ulsan, Korea, and its recoverable reserve is expected to be 170 to 200 BCF (Billion cubic feet). The field was confirmed to have potential gas and condensate reserves from an exploration well in 1998 and two appraisal wells in 1999. This field consists of five zones, with an average reservoir depth of about 7,000 to 8,000 ft. In this study, we have performed an analysis of Gorae V DST (Drillstem test) #2 for testing B4 zone which has the biggest reserves and Gorae V-1 DST #2 for testing B3 and B4 zones simultaneously among DST data achieved in a total of 11 zones at three wells. The pressure and flow rate recorded from two tested zones were used to obtain the reservoir characteristics and the well productivity. For pressure transient test data, we carried out the analysis of reservoir permeability, skin factor, wellbore storage effect and barrier effect by using the Homer plot and type curve matching methods. Also, with the deliverability test data, we estimated the absolute open flow which is the maximum flow rate of the gas well, and extracted the correlations representing production rate with reservoir pressure. According to the analysis, Gorae V DST #2 of B4 zone has a permeability and skin factor of 37 md (Millidarcy), 4.54, and Gorae V-1 DST #2 of B3 and B4 zones has 23 md and 21.0, respectively. It was also found that the wellbore storage effect was not significant for the two wells tested. From the deliverability test analysis, the AOF (Absolute open flow) of the Gorae V DST #2 is 152.8 MMSCFD (Million standard cubic feet per day), and that of the Gorae V-1 DST #2 is calculated to be 68.2 MMSCFD.     

以产量为目标的水平井最优井筒长度

目前在研究水平井水平段长度优化时,大多采用Dikken优化原则,即当摩擦损失减少了20%产能时的长度为最优水平井长度。考虑水平井筒内的摩擦压降的同时,建立了油藏内流动模型、水平井井筒内流动模型、耦合水平井与油藏渗流,利用井筒内流体质量守恒定律,以产量为目标推导了油藏水平井水平段最优长度公式。对其敏感性参数作了分析并讨论摩擦压降对产能的影响。该模型既可以确定合理的水平井筒段长度,同时对水平井长度的优化设计具有指导意义。     

用测井资料确定产层参数

本文详细介绍了用测井资料来确定井点各产层的剩余油饱和度、供液边界压力、渗透率和表皮系数的方法，并用实例来证实了该种方法的可行性，评价结果与实际生产情况基本一致。     

井筒变质量流与油藏渗流耦合参数研究

为进一步研究水平井筒变质量流与油藏渗流的耦合流动,本文将复杂的油藏—井筒区域流体动力学问题转化为油藏渗流、井筒附近Brinkman渗流和井筒管流3种流动形式的耦合问题,建立了油藏—井筒耦合流体动力学有限元数值模型,采用多物理场耦合软件COMSOL对所建模型进行求解。定量描述了油藏—井筒区域流动形态,并分析了储层渗透率、原油动力粘度、井径、井长等因素对井筒内压力损失和井筒入流剖面的影响规律。     

低渗透油藏压力传播特征分析

基于鸭儿峡低渗透油藏注水开发的基本生产特征,即注水压力不断升高、注水量不断降低、油井供液不足、产量递减快、采油速度低,对具体井组进行试注效果分析,发现油井主要依靠弹性介质传递能量,最终实现增油目的。针对低渗透储集层存在启动压力,且注水能量主要消耗在井筒附近,压力具有先累积后缓慢释放的传播特征,考虑到低渗透储集层压力传播特征,建议对地层进行压裂和周期注水以调整储集层压力的重新分布,降低注水井注入压力。通过对比分析周期注水与常规注水效果,发现周期注水采出程度高,开发效果好。     

射孔水平井流入动态分析

水平井有很复杂的几何流动形态,某种程度上是由于主流动区和沿井筒的流体之间的相互作用和完井类型引起的。文中针对底水驱油藏利用射孔完井的水平井生产时单相原油三维稳态流动的压力分布公式,分析了射孔数量、井筒长度、体积系数等参数与井产量之间的关系,利用cholesky分解法求解了线性方程组,求得了射孔水平井的产量以及水平井产量与水平井长度流体粘度、水平井射孔数目及原有体积系数的关系曲线。     

考虑水平井井筒摩阻效应的数值模拟研究

水平井井筒流动与直井有着明显区别。水平井水平段的流动为变质量流动。需要考虑井筒摩阻效应对水平井产能的影响。本文主要应用E clipse软件中的多段井模拟技术,研究在考虑井筒摩阻情况下,水平井井筒的流动规律。在靠近水平井井筒趾端的位置,压力变化较小,越靠近跟端,压力变化越大。从开发指标看:随着趾端注入量的增加,无水采出程度增加,达到1.2~1.3倍时最大,而后又开始下降。     

异常高压气藏动态预测研究

在异常高压气藏开发过程中,由于应力敏感性造成的渗透率变化无法忽略,因此在建立二项式渗流方程时必须考虑由于应力敏感性造成的渗透率的变化情况,定义新的拟压力形式的渗流方程。再以物质平衡原理为基础,导出定容异常高压气藏的压降方程,并与井筒流动方程相结合,建立动态预测模型。由于该模型很好的考虑到了应力敏感性造成的影响,使得更适用于实际生产过程中,对于异常高压气藏生产动态的预测有较好的效果。     

Helical Flow of a Sutterby Model Fluid

The problem of helical flow of a Sutterby model fluid has been analyzed numerically using a finite difference technique. Sutterby model fluid is one of the most important non-Newtonian fluids representing constitutive equations for high polymer aqueous solutions of CMC, HEC, and MC, and hence the problem is of practical significance. Computations have been made for the case when the inner cylinder rotates about the common axis with constant angular velocity and the outer cylinder is at rest, while a constant pressure gradient is acting on the axis of rotation. The dimensionless velocity profiles, volumetric flow rate, torque, and pressure distribution have been calculated for various values of the model parameters and the radius ratio.     

变流量法确定油藏地层参数

本文详细介绍了如何通过改变井口流量来确定多油层井中各小层的地层压力、渗透率和表皮系数等参数的方法,并用实例来验证了该种方法的可行性。     

Numerical flow simulation of viscoplastic fluids in annuli

This paper describes numerical solutions for the laminar flow of non-Newtonian fluids in vertical annuli using the Herschel-Bulkley model to describe the rheological behaviour of such materials. Numerical solutions have been obtained when there is both axial and tangential flows in either a concentric or eccentric annulus. The tangential flow arises from the rotation of the inner cylinder of the annulus and the axial flow from a constant axial pressure gradient. The flow is analysed by solving the momentum and continuity equation numerically using the finite element method. The dimensionless velocity, deformation and stress profiles with other quantities such as the apparent viscosity and pressure distribution have been calculated for various eccentricities, radius ratios, fluid properties and flow parameters; the results give insights into the flow behaviour in the annuli. It is shown that the inclusion of rotational effects, for a fixed pressure gradient, is likely to increase the axial volumetric flowrate over non-rotating situations in concentric geometries. New results reveal that, in eccentric annuli, the situation is reversed and the flowrate gradually decreases as the rotation rate is increased.     

萨中开发区地层脱气影响流压界限研究

大庆萨中油田目前已进入高含水后期,通过放大生产压差来满足体液稳产的需要,同时可以避免油井生产压差过大,对井底流压造成偏低,是的油层严重脱气,对单井和区块的产能有影响,因而通过研究区块和单井的合理流压界限,平衡采油速度、提高开发效果是非常有必要的。在研究萨中东区各油井生产动态基础上,通过地质统计学和油藏工程、渗流力学等方法,来确定该区块的合理流压界限,通过计算对比与实际应用发现效果良好,同时该技术的研究方法对同类油田的研究具有一定的指导和借鉴意义。     

水平井延缓底水锥进梯级筛管完井技术研究

开采底水油藏最大的技术难题是如何有效地控制和延缓底水锥进。虽然延缓底水锥进的技术众多,但利用梯级筛管实现控水的技术研究甚少。本文基于油藏渗流与井筒管流耦合模型和基管上泄流孔孔眼摩阻计算模型,建立了梯级防砂筛管完井的油藏-井筒-孔眼耦合数学模型。在此数学模型的基础上,编制了用于延缓底水的梯级防砂筛管优化设计程序。该程序可以计算梯级筛管完井方式下的水平井筒压力剖面并且可以优化基管上的孔密和孔径。通过设计合理的孔密和孔径,可以判断梯级防砂筛管能否起到"井下油嘴"的调节作用,从而有效地设计出水平井梯级防砂筛管的结构。     

水平井延缓底水锥进梯级筛管完井技术研究

开采底水油藏最大的技术难题是如何有效地控制和延缓底水锥进。虽然延缓底水锥进的技术众多,但利用梯级筛管实现控水的技术研究甚少。本文基于油藏渗流与井筒管流耦合模型和基管上泄流孔孔眼摩阻计算模型,建立了梯级防砂筛管完井的油藏-井筒-孔眼耦合数学模型。在此数学模型的基础上,编制了用于延缓底水的梯级防砂筛管优化设计程序。该程序可以计算梯级筛管完井方式下的水平井筒压力剖面并且可以优化基管上的孔密和孔径。通过设计合理的孔密和孔径,可以判断梯级防砂筛管能否起到"井下油嘴"的调节作用,从而有效地设计出水平井梯级防砂筛管的结构。     

A Hydrodynamic Modei for Slug Frequency in Horizontal Gas-Liquid Two-Phase Flow

The prediction of slug frequency has important significance on gas-liquid two-phase flow. A hydrody-namic modei was put forward to evaluate slug frequency for horizontal two-phase flow, based on the dependence of slug frequency on the frequency of unstable interfacial wave. Using air and water, experimental verification of the modei was carried out in a large range of flow parameters. Six electrical probes were installed at different positions of a horizontal plexiglass pipe to detect slug frequency development. The pipe is 30m long and its inner diameter is 24 mm. It is observed experimentally that the interfacial wave frequency at the inlet is about l to 3 times the frequency of stable slug. The slug frequencies predicted by the modei fit well with Tronconi (1990) modei and the experimental data. The combination of the hydrodynamic modei and the experimental data results in a conclusion that the frequency of equilibrium liquid slug is approximately half the miniraum frequency of interfacial wave.     

应力敏感油藏中考虑启动压力和二次梯度的非线性渗流模型

从质量守恒原理出发,详细推导出了应力敏感油藏中考虑启动压力梯度和二次压力梯度非线性不稳定渗流偏微分方程。并通过变量代换,将渗流方程拟线性化,最后利用Douglas-Jones预估一校正法求得模型的数值解。讨论了不同参数变化时井底压力的变化规律,做出了典型压力曲线图版。曲线在形态和特征上与线性模型曲线明显不同,不再遵循“0．5线”规则和“单位斜率”规则。启动压力梯度因子影响压力降落曲线晚期上翘段的斜率,该因子越大,曲线上翘程度越大,当其很小时,压力导数曲线出现水平直线段。     

Flow rate measurement errors in vacuum tubes: Effect of gas resistance to accumulation

Accumulative flow of gas into a vacuum tube has been studied. An analytical model, based on Fick's second law and assuming a constant diffusion coefficient, has been developed to describe the pressure response as a function of time and tube axial position for a constant gas flow rate into a closed vacuum tube. The predicted non‐linear pressure response was verified by conducting short‐term experiments involving a constant gas flow into an instrumented vacuum tube. Initially, the error in flow rate determined using the pressure rise technique was as much as ±100%. At longer time intervals, the constant diffusion coefficient assumption is invalid and the empirical model of Knudsen is used to describe the dependence of the diffusion coefficient on pressure. The governing partial differential equation was solved numerically. The numerical solution accurately predicts the pressure response at any time interval.     

Concentration profiles of reactant in a viscous finger formed during the interfacially reactive immiscible displacements in porous media

A simple unsteady-state convective-diffusion model was employed to simulate reactant concentration profiles in a viscous finger, which is created during interfacially reactive displacement of two immiscible fluids in porous media. A two-dimensional system was considered. It was assumed that the finger grew in one direction at a constant flow rate and that a fast chemical reaction was taking place at the oil–water interface layer. Interaction with reservoir rock was also taken into account. Two types of convective flow were studied: steady-state laminar flow with a parabolic velocity profile and plug flow with a flat velocity profile. The numerical method of lines was used to solve the model equation. A significant decrease of reactant concentration in the water phase, especially in the fingertip area was observed. This can cause important changes in interfacial behavior and influence the efficiency of fluid displacement. The model numerically confirmed previous visual observations of displacing patterns during the displacement of acidified oil by alkaline solutions.     

封闭多井油藏中的压力恢复分析

A general method has been developed for analyzing pressure buildup data from a well located in a system with both production and injection wells in a closed, bounded two-phase flow reservoir. The proposed method enables one to calculate the total mobility or permeability-thickness product, the skin factor, the average drainage-area pressure and the injection-production ratio （at the instant of shut-in） with accuracy from pressure buildup （or falloff） data dominated by a linear trend of reservoir pressure. Out of thousands of well tests, several typical field examples have been presented to illustrate the application of the proposed method for analyzing pressure transient data from a well located in a water-injection multiwell reservoir. And the possible application of this method to heterogeneous systems such as naturally fractured reservoirs is also discussed. Approaches to aid practicing engineers in verifying the buildup interpretation （or recognizing the interference of offset wells） are presented. Extension of the presented method to a gas well located in a multiwell gas reservoir is also suggested     

上置加热管筛板蒸发器流体力学及蒸发性能

对筛板上方液层内置有水平加热管束的载气蒸发器的流体力学和蒸发性能进行了实验研究,并对实验结果进行了分析。结果表明,在气速一定时,筛板单板阻力随着液体流量的增大而提高;在液体流量一定,气速较大时筛板单板阻力不随气速而变化;随着液体温度的提高,筛板单板阻力明显减小;在相同条件下,上置管束的筛板单板阻力比普通筛板单板阻力明显增大。对于常温下的空气水体系,在相同条件下,加热管束通入加热蒸汽可使出口空气的湿含量提高8. 7%—12. 6%。随着加热管束通入蒸汽流量的增加,出口空气的湿含量进一步提高。