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1、The Proposal of Formation Pressure Monitoring in South Azadegan Oilfield1. ObjectivesFormation pressure (static pressure) is an important dynamic parameter reflecting reservoir energy levels. Through regular measurement of formation pressure, we can understand the changes of formation pressure, and
2、analyze reservoir development performance accurately.In order to understand the performance of Early Production wells in South Azadegan oil field and make a reasonable evaluation of S/K/G/F reservoirs, it is necessary to select a number of representative Early Production wells for pressure buildup t
3、esting. In the mean time, the static pressure point on new wells which will be put into production should be measured. Purposes are summarized as follows:1) Determine formation pressure，formation temperature, flowing pressure and flowing pressure gradient.2) Analyze the production performance of tes
4、ted well, determine the productivity of tested well, choose an optimal flow rate. 3) Calculate the physical characteristic parameters, such as effective permeability of reservoir, understand the heterogeneity .4) Calculate skin factor of wellbore to provide information for implementing stimulation.2
5、. Well Selection PrinciplesThe wells selected for formation pressure monitoring should meet the following requirements:1) Being representative of the different reservoir (Sarvak, Kazhdumi, Gadavan and Fahliayn).2) Being representative of the different well location (South, Middle and North region).3
6、) Being representative of the different well type (vertical and horizontal).4) Considering the production history , including production time, production rate and wellhead pressure. 5) Well head and downhole string can meet the requirement for testing.Considering above principles, the following well
7、s are selected for conducting regular formation pressure monitoring.Table 2.1 Monitoring wells in Sarvak reservoirWellIntervalWell TypeLocationProduction Rate(bbl/d)WHP（psi）Production Time(month)AZN-02S-3-5sidetrackmiddle81526060AZN-05S-3-4verticalnorth182662059AZN-63-4-5vrticalsouth316056059AZN-16S
8、-4deviatednorth76225041AZN-22S-3horizontalmiddle73728026Table 2.2 Monitoring wells in K/G/F reservoir WellReservoirWell TypeLocationProduction Rate (bbl/d)WHP(psi)Production Time(month)AZN-21K-2bverticalnorth1570110034AZN-12G-3sidetracksouth248792044AZN-11F-3sidetrackmiddle 3. Testing Method and Req
9、uirementsIn order to achieve the above objectives, transient pressure buildup testing is the best choice. 1) RIH two tandem memory electronic pressure gauges at the speed of 60m/min to the mid-depth of pay zone with slickline operation to obtain pressure and temperature data. 2) Flowing and static p
10、ressure and temperature gradient must be measured when RIH pressure gauge. Pressure and temperature gradient should be measured every 200m to the depth of 1000m and every 100m to the destination depth. The destination depth is mid-depth of pay zone or as near as possible to the mid-depth of pay zone
11、. For horizontal well, the destination depth is KOP . The measuring time for each point must be longer than 5 minutes. 3) The production rate of well test must be stable, the fluctuation of flow rate in three (3) days before testing should be within 5% of the average flow rate.4) There is no leakage
12、 on well head assembly, the valves are all installed and work properly.5) Pressure gauge used in testing must meet following requirements, maximum rated pressure 10k PSI, accuracy 0.02%, resolution 0.01PSI. 6) Testing data must be interpreted by advanced interpretation software such as Pan System or
13、 Saphir.7) Formation pressure should be tested semiannually, time interval between two testing should be more than 4 months.4. Optimization of Shut in Time for Buildup Testing4.1 Well Testing History of Early Production Wells33 times buildup testing have been conducted in S/K/G/F reservoir, and 16 o
14、f them can not be interpreted due to that shut in time was too short, around 3.5-49 hours, the radial flow did not appear, reservoir parameter and reservoir boundary conditions was unable to interpret. The following example is a buildup testing of AZN-5 well. Fig 4.1 Build up testing of Sar-4-6 in A
15、ZN-5 wellTable 4.1 Parameters for interpretation of Sar-4-6 in AZN-5 wellProd.time（h）46Effec. thickness(m)79Compressibility factor(psi-1)0.0000191Ave.oil rate(bbl/d)3135Por(%)11.5Well modelverticalbuild up time(h)162Volume factor1.38Reservoir modelTwo porosity SlabWell radius(in)7Viscosity(cp)5.95Boundary modelinfiniteTable 4.2 Interpretation of Sar-4-6 in AZN-5 (double porosity reservoir)Pi(psi)Formation coefficient (md.ft)Effective Perm.(md)SkinBoundary462957200290-2.840.06862.23E-06sh
