Many naturally fractured reservoirs are composed of matrix, fractures, and nontouching vugs (there can also be any other type of nonconnected porosity that can occur; for example, in intragranular, moldic, and/or fenestral porosity). An improved triple-porosity model is presented that takes these different types of porosities into account. The model can be used continuously throughout a reservoir with segments composed of solely matrix porosity, solely matrix/fractures, solely fractures/vugs, or the complete triple-porosity system.The model improves a previous triple-porosity algorithm by handling rigorously the scale associated with each: matrix, fractures, and vugs. This permits determining more-realistic values of the cementation or porosity exponent, m, for the composite system and consequently improved values of water saturation and reserves evaluations. The values of m for the triple-porosity reservoir can be smaller than, equal to, or larger than the porosity exponent of only the matrix blocks, m b , depending on the relative contribution of the vugs and fractures to the total porosity system.It is concluded that not taking into account the contribution of matrix, fractures, and vugs in the petrophysical evaluation of triple-porosity systems can lead to significant errors in the determination of m, and consequently in the calculation of water saturation, hydrocarbons in place, and recoveries, and ultimately can lead to poor economic evaluations-either too pessimistic or too optimistic. This is illustrated with two examples from Middle East carbonates.

Many naturally fractured reservoirs are composed of matrix, fractures and non-touching vugs (it can also be any other type of non- connected porosity that can occur, for example, in intragranular, moldic and/or fenestral porosity). An improved triple porosity model is presented that takes into account these different types of porosities. The model can be used continuously throughout a reservoir with segments composed of only matrix porosity, or only matrix-fractures, or only fractures-vugs, or the complete triple porosity system. The model improves a previous triple porosity algorithm by handling rigorously the scale associated with each, matrix, fractures and vugs. This permits determining more realistic values of the cementation or porosity exponent, m, for the composite system and consequently improved values of water saturation and reserves evaluations. The values of m for the triple porosity reservoir can be smaller, equal to, or larger than the porosity exponent of only the matrix blocks, mb, depending on the relative contribution of the vugs and fractures to the total porosity system. It is concluded that not taking into account the contribution of matrix, fractures and vugs in the petrophysical evaluation of triple porosity systems can lead to significant errors in the determination of m, and consequently the calculation of water saturation, hydrocarbons in place, recoveries, and ultimately poor economic evaluations, either too pessimistic or too optimistic. This is illustrated with a couple of examples from Middle East carbonates.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractField cases presented on this paper explain applications of Mechanical External Casing Packer (MECP) solving zonal isolation problems on openhole horizontal wells in Saudi Aramco. MECP is essentially a hybrid between existing casedhole conventional packer and inflatable External Casing Packer (ECP). MECP is different than ECP in the mechanism energizing the sealing element. The packer is run as an integral part of the casing string to provide a seal between the casing and wellbore. Saudi Aramco has successfully used MECP controlling water production, isolating fractured openhole sections, sealing casing shoe with leaking problem, and compartmenting openhole horizontal section.Included in this paper are four different field cases for openhole zonal isolation with MECP on horizontal wells. Each field case presents a particular application for the MECP. Technical data including well configuration and casing string are included in the paper. Field operations and lesson learned from each application are also presented in this paper.MECP has been successfully used for zonal isolation on openhole horizontal wells. Depending on the particular application, MECP can be run in combination with blank and/or screened pipe. Hole cleaning and wellbore conditions are factors affecting MECP placement.The knowledge provided in the paper can be applied to solving zonal isolation problems on openhole horizontal sections with different rock and fluid properties. The significance of this paper is that it presents actual field experiences and lessons learned for MECP applications. Furthermore, recommended field operations for successfully placing MECP on the well are also included in this paper.

A previously defined triple porosity model is used to calculate the cementation exponent (m) of complex carbonate reservoirs in the Middle East using well log data. The cementation exponent is usually affected in carbonate rocks by different types of primary and secondary porosities. A combination of interparticle porosity, non-connected porosity (e.g., vuggy and fenestral) and fractures increases the uncertainty in the estimation of m. Therefore, a well-defined petrophysical approach must start by first understanding the rock's fabric. Initially, samples are classified into different flow units based on pore throat apertures at 35% cumulative pore volumes (rp35). This classification is then extended to include variations in porosity types based on geological and petrophysical descriptions of each rock. Each sample has different proportions of connected and non-connected porosities. These porosities are defined as matrix, fractures and non-touching vugs (including fenestral porosity). The porosity types are extracted from well logs for the whole reservoir section and are cross-checked against core samples and thin sections. The value of m in a triple porosity system can be larger, equal, or smaller than the cementation exponent of only the matrix blocks (mb). This variation depends on the relative contribution of natural fractures and non-touching vugs compared to the composite triple porosity reservoir. A continuous curve of m values is obtained using this model. A good comparison has been obtained between the results of this model and m values measured in the laboratory. Estimation of variable m values within short distances in a given reservoir using the triple model is a significant development in formation evaluation that helps reduce uncertainty in petrophysical calculations. The results increase the confidence level in water saturation and reserves determinations.

Field cases presented on this paper explain applications of Mechanical External Casing Packer (MECP) solving zonal isolation problems on openhole horizontal wells in Saudi Aramco. MECP is essentially a hybrid between existing cased-hole conventional packer and inflatable External Casing Packer (ECP). MECP is different than ECP in the mechanism energizing the sealing element. The packer is run as an integral part of the casing string to provide a seal between the casing and wellbore. Saudi Aramco has successfully used MECP controlling water production, isolating fractured open-hole sections, sealing casing shoe with leaking problem, and compartmenting openhole horizontal section. Included in this paper are four different field cases for openhole zonal isolation with MECP on horizontal wells. Each field case presents a particular application for the MECP. Technical data including well configuration and casing string are included in the paper. Field operations and lesson learned from each application are also presented in this paper. MECP has been successfully used for zonal isolation on openhole horizontal wells. Depending on the particular application, MECP can be run in combination with blank and/or screened pipe. Hole cleaning and wellbore conditions are factors affecting MECP placement. The knowledge provided in the paper can be applied to solving zonal isolation problems on openhole horizontal sections with different rock and fluid properties. The significance of this paper is that it presents actual field experiences and lessons learned for MECP applications. Furthermore, recommended field operations for successfully placing MECP on the well are also included in this paper. Introduction Mechanical External Casing Packers and External Casing Packers have been successfully used for solving different problems in drilling and completion operations in Saudi Aramco. Mechanical External Casing Packer description. Mechanical External Casing Packer (MECP) is primary a cementing and zone isolation systems utilizing a non-inflatable packing element (Fig. 1). The packer is run as an integral part of the casing string to provide a seal between the casing and wellbore. MECP has an elastomeric element which is set mechanically by shifting a balance sleeve allowing wellbore hydrostatic pressure to flood an atmospheric chamber and apply setting force to the non-inflatable element. The element is hydrostaticly set by mechanically shifting a sleeve, using an inner work string with a shifting tool on its bottom, and then mechanically locked.1 MECP is essentially a hybrid between existing cased-hole conventional and inflatable External Casing Packer (ECP).2 MECP was initially trial tested for zonal isolation on well A-41 at Heidrun field. Heidrun is located on the Haltenbanken area of the Norwegian Sea. The upper part of the reservoir is produced with aid of water and gas injection. Production from the lower part of the reservoir is based on water injection. Well A-41 has a 320 meter long 8–1/2 in. openhole section. The openhole liner consisted of 11 joints of Baker 5–1/2 in. Excluder coarse screen, one MECP and four additional joint of screen above the packer. No operational problem was reported during the trial test.2 MECP has been used, in combination with Inflow Control Devices (ICD) and blank pipe, to separate regions with different rock and fluid properties across the horizontal section. ICD were developed to create an uniform production profile along the entire horizontal section of the well.3, 4, and 5 ICD can be a pipe-joint with layers of different screen-size on top of each other (Fig. 2). ICD is designed to optimize production and delay water or gas coning in long, low-drawdown, high-rate horizontal wells.6, 7, and 8 External Casing Packer (ECP) Description. ECPs and Annulus Casing Packers (ACPs) are inflatable packers that are also run as an integral part of the casing string. They must be inflated during the completion installation. When inflated, they provide an annular seal between the casing and the wellbore or a previous installed casing string. The packers are designed for inflation with fluid (cement, drilling mud or water).9 As long term application requires cement inflation to minimize adverse effects on the packer, also the installation process is further complicated, especially in a highly deviated and horizontal wellbore.2, 10