FaultAnalysis

1、Fault Analysis 定 义 断层断层是岩石破裂的一个面或一个带，在这个面或带上，存在一定的位移。这个面或带上，影响流体流动和分布的参数与附近其它地方会有些不同。 断层封堵与流体流动和分布有关的断层面上或带上的封堵性。断层可能是起阻挡作用的也可能是横向泄漏的或垂向起通道作用的。基本的断层封堵概念(1)断层对油气运移既可起封堵作用也可起通道作用；(2)断层封堵性沿着断层上下左右可能是变化的，并且是暂时的；(3)断层在倾向上或横向上都可能产生封堵或泄漏；(4)断层可能在特殊的一边通过油气相优先产生封堵；(5)断层封堵能用油气聚集的静态或稳定状态下的断层圈闭的油气充填的几何形态中推论；(6)

2、断层封堵受许多相互交错联系的地质可变因素的影响；(7)断层封堵以及储层顶部盖层，对流体来说并不是绝对起阻挡作用的，只要经过足够的时间，最终是要泄漏的。进行断层封堵分析的理由(1)探区内有意义地区和生产油田是以断层为界或是断块；(2)断层全部或部分控制油气圈闭的地层；(3)在探区内断层是主要的圈闭因素；(4)切割某油田的断层的封堵作用指出了该油田是在流体运移还是起划界作用；(5)断层封堵的预测在勘探和开发中具有同等的重要性。断层封堵分析的应用1)熟练的断层封堵钻前预测：2)在断块远景区里进行油气量的合理评估；3)在钻探断层圈闭中减小风险和提高成功率；4)断块油田的有效开发 5)依靠断层圈闭的新探

3、区的描述 6)对世界范围内的其它盆地的推测。断层封堵机理(1)并置作用，储集砂岩与排替压力很高的低渗地层单元(如页岩)并置；(2)黏土涂抹，即黏土或页岩挤入断层面，因而赋予断层本身很高的排替压力；(3)碎裂作用，砂岩颗粒破碎形成细粒的断层泥再赋予断层一个很高的毛细管排替压力；(4)成岩作用，沿最初可渗透断层面优先发生的胶结作用可能使孔隙度部分或完全消失，最终形成一个水力封堵transmissibility multipliers Faults are often critical areas of a reservoir model. While they represent a relati

4、vely small part of the total volume, they can strongly influence the permeability and the drainage patterns. Many simulators use the concept of transmissibility multipliers across faults to avoid having to model the fault volume explicitly. The Eclipse suite uses such multipliers to model the effect

5、 of faults Fault classification Based on the geologic history of each fault, it may be defined as: sealing - transmissibility multiplier of 0 open - transmissibility multiplier of 1 partially sealing - transmissibility multiplier between 0 and 1 variably sealing - transmissibility multiplier depends

6、 on local geological constraints. Faults may also be modeled as sealing until a defined Threshold Pressure is reached. The first step of the workflow is to group sets of faults which are expected to have similar properties shale content of the host rocks lithification state at the time of faulting.

7、geologic conditions during and after the time of faulting (stress state, temperature, hydrothermal fluids, etc.), the type of faulting (normal, reverse, strike-slip, or combination), and whether the faults have experienced a complex motion history with multiple episodes of displacement under differe

8、nt conditions. Fault property calculations If you have identified any faults as variably sealing, then the fault transmissibility must be calculated. This in turn requires the definition of fault permeability and thickness. Shale gouge ratio is only required if the permeability is calculated using M

9、anzocchis equation There are a number of methods to calculate those properties based on displacement, shale gouge ratio, rock type, etc. Depending on the method employed, these intermediate properties may need to be calculated.There are four basic methods used to calculate properties1.Constant value

10、: provide a constant value for the property 2.Proportional to throw: the property is proportional to the throw on the fault either directly or via a log relationship. 3.Lithology proportional weighting: Values will be given for each facies in the geological grid. The value for each face cell in the

11、fault will be calculated based on the cells which have slid past it during history. See Displacement weighted mean. 4.Lithology juxtaposition: Values will be given for each pair of juxtaposed facies. The dialog has one tab for each of the parameters to be estimated:Permeability: the permeability of

12、the fault Shale: the shale ratio of the material in the fault. Only required if the standard equation is used for fault permeability. Thickness: the thickness of the fault body. Grid Properties: the permeability and net-to-gross of the grid. Used for the calculation of the transmissibility multiplie

13、r. Property calculations are accessed by pressing the calculation button next to the calculated option on the Fault Analysis dialog Fault property calculations Permeability tabPermeability tab (Fault property calculations) There are four options for calculating fault permeability.Constant: permeabil

14、ity is assigned directly. This option can be used with IJK faults . Standard Equation: permeability is calculated based on shale content and displacement using an equation defined by Manzocchi et al., 1999. Lithology proportional: Values will be given for each facies in the geological grid. The valu

15、e for each face cell in the fault will be calculated based on the cells which have slid past it during history. See Displacement weighted mean. Lithology juxtaposition: Values will be given for each pair of juxtaposed facies. . Displacement weighted meanFor some of the methods (e.g. the Lithology pr

16、oportional method for computing fault permeability) the resulting property is displacement weighted. This means that when a property is computed, a value is first assigned to each facies type. The final property value for the fault face cell is then computed as an average of the values of all cells

17、which that fault face has moved past. This method models the smearing of properties along the fault. It is assumed that the fault movement is parallel to the fault pillars.Shale tabShale tab (Fault property calculations) Shale calculations are necessary when permeability is calculated using the Stan

18、dard Equation option, and so these options are not applicable to IJK faults . There are three options for calculating Shale ratio:Constant: shale ratio is assigned directly From grid property: shale ratio is calculated based on a net to gross or volume shale property in the grid. This accounts for c

19、ells which have moved past the fault face cell during faulting, see Displacement weighted mean for an explanation of this averaging. Lithology dependent: shale ratio is calculated based on a discrete property in the grid (e.g. facies). A value is assigned to each facies code, and a value is assigned

20、 to each fault face cell, based on the cells which have moved past this face during faulting, see Displacement weighted mean for an explanation of this method.Thickness tabThickness tab (Fault property calculations) There are three options for calculating fault thickness:Constant: fault thickness is

21、 assigned directly. This option can be used with IJK faults . Proportional to throw: fault thickness is equal to the displacement on the fault multiplied by a constant. It is also possible to make thickness equal to the log of the displacement multiplied by the constant. This option cannot be used w

22、ith IJK faults. Lithology dependent: shale ratio is calculated based on a discrete property in the grid (e.g. facies). A value is assigned to each facies code, and a value is assigned to each fault face cell, based on the cells which have moved past this face during faulting, see Displacement weight

23、ed mean for an explanation of this method. This option cannot be used with IJK faults. Grid Properties tab Grid Properties (Fault property calculations) Specify the net-to-gross and permeability properties in the grid to be used in the calculation of transmissibility multipliers. The same properties

24、 as those used for the simulation must be selected. Otherwise, different input is provided for computing the grid cell transmissibility and the fault transmissibility. If permeability tensors are available, then they may be specified in I, J and K directions (K permeabilities are only used for IJK f

25、aults and are otherwise optional).Calculating Transmissibility Multipliers Once fault permeabilities and fault thicknesses have been calculated, the transmissibility multipliers can be calculated. Those are the required input for the simulator.Petrel will first calculate the transmissibility between

26、 the centers of the two cells on either side of the fault without taking into account the fault itself. This calculation is based on the geometry of the two cells, the permeability of these two cells and the geometry of the fault face cell (the common area on the side adjoining the two cells).Petrel

27、 will then calculate the transmissibility between the two cells again, this time taking into account the permeability and the thickness assigned to the fault face cell, which is itself made up of two sides (see Fault property calculations). This second transmissibility will be divided by the first to give the transmissibility multiplier to be gi