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Home My WebLink About2004 Northstar Oil Pool Annual Reservoir Performance Report Northstar Field Northstar Oil Pool January 2004 through December 2004 2 Table of Contents A. Progress of Enhanced Recovery Project B. Voidage Balance by Month of Produced Fluid and Injected Fluids C. Summary and Analysis of reservoir pressure surveys within the pool D. Results and Analysis of Production and Injection Log surveys, tracer surveys, observation well surveys and any other special monitoring. E. Review of pool production allocation factors and issues over the prior year F. Review of Annual Plan of Operations and Development and Future Development Plans G. Status of wells shut -in for 365 days or more Attachment 1: Map of well Locations Attachment 2: Northstar Field 2004 Overview Statistical Summary Attachment 3: Corrected 2003 Voidage Balance by Month of Produced Fluid and Injected Fluids Attachment 4: Northstar Field 2004 Reservoir Pressure Report, Form 10-412 3 A) Progress of Enhanced Recovery Project During 2004, two additional production wells (NS16 and NS21), one additional gas injection well (NS25) and one Class I disposal well (NS32) were brought on line. Average oil production was 68,520 bopd and average miscible gas injection was 359.3 mmscfd. Miscible injection gas consisted of produced formation gas containing NGLs and imported make-up gas from Prudhoe Bay. The location of these wells and other wells that have been added to date are shown in Attachment 1. Production and injection statistics are summarized in Attachment 2. During 2004, gas injection was just slightly less than reservoir voidage. At year end, the reservoir had an overall voidage replacement ratio of 0.9985. 4 B) Voidage Balance by Month of Produced Fluid and Injected Fluids Month Oil, MRB Free Gas, MRB Water, MRB Total Voidage, MRB 2004 Cum, MRB Cum since start-up, MRB Formation Gas, MRB Import Gas, MRB Total Injection, MRB 2004 Cum, MRB Cum since start-up, MRB Net Injection, MRB 2004 Cum, MRB Cum since start-up, MRB January-04 5,191 1,315 184 6,690 6,690 120,545 4,932 2,043 6,975 6,975 121,187 285 285 642 February-04 2,426 651 91 3,168 9,858 123,713 2,339 1,511 3,850 10,825 125,037 682 967 1,325 March-04 4,792 1,704 183 6,678 16,536 130,391 5,040 1,969 7,009 17,834 132,046 330 1,298 1,655 April-04 4,047 1,705 172 5,924 22,460 136,315 4,522 1,291 5,813 23,646 137,859 -111 1,186 1,544 May-04 4,971 3,294 201 8,466 30,926 144,781 6,755 1,437 8,192 31,839 146,051 -273 913 1,270 June-04 4,656 3,175 252 8,084 39,010 152,865 6,414 889 7,302 39,141 153,353 -782 131 488 July-04 4,607 3,802 278 8,687 47,697 161,552 7,005 912 7,917 47,058 161,270 -770 -639 -282 August-04 3,274 2,033 211 5,518 53,215 167,070 4,287 1,333 5,620 52,678 166,890 101 -538 -180 September-04 4,873 3,627 324 8,823 62,038 175,893 7,017 1,853 8,870 61,548 175,760 47 -490 -133 October-04 4,909 3,548 374 8,830 70,868 184,723 6,962 1,766 8,729 70,277 184,489 -101 -591 -234 November-04 4,711 4,168 330 9,209 80,077 193,932 7,450 1,920 9,370 79,647 193,859 161 -430 -73 December-04 4,906 4,731 368 10,005 90,082 203,937 8,147 1,627 9,774 89,421 203,633 -231 -661 -304 2004 Totals 53,363 33,753 2,966 90,082 70,870 18,551 89,421 -661 Produced Fluids Injected Fluids Net Injection (Injection - Production) Note: MRB stands for thousand reservoir barrels Note: The 2003 Voidage Balance Table had a slight calculation error. The corrected 2003 Voidage Balance Table is presented in Attachment 3. 5 C) Summary and Analysis of reservoir pressure surveys within the pool Static bottom hole pressures collected in 2004 are summarized below. Well Date Extrapolated Pressure at -11,100' TVDss Datum, psia Data Source NS20 16-Feb-04 5,230 SBHP NS18 17-Feb-04 5,199 SBHP NS15 19-Feb-04 5,208 SBHP NS06 21-Feb-04 5,197 Cidra Data NS12 21-Feb-04 5,162 Cidra Data NS13 21-Feb-04 5,212 Cidra Data NS14 21-Feb-04 5,227 Cidra Data NS16 21-Feb-04 5,217 Cidra Data NS22 21-Feb-04 5,179 Cidra Data NS24 21-Feb-04 5,226 Cidra Data NS25 13-Apr-04 5,110 SBHP NS13 13-Apr-04 5,222 Cidra Data NS22 13-Apr-04 5,180 Cidra Data NS24 24-Apr-04 5,224 Cidra Data NS14 17-May-04 5,211 Cidra Data NS24 10-Jun-04 5,197 Cidra Data NS21 15-Jun-04 5,198 Cidra Data NS14 23-Jun-04 5,180 Cidra Data NS13 11-Jul-04 5,183 Cidra Data NS24 11-Jul-04 5,190 Cidra Data NS06 11-Jul-04 5,154 Cidra Data NS14 11-Jul-04 5,175 Cidra Data NS21 8-Aug-04 5,164 Cidra Data NS06 8-Aug-04 5,146 Cidra Data NS16 8-Aug-04 5,140 Cidra Data NS22 8-Aug-04 5,139 Cidra Data NS13 8-Aug-04 5,171 Cidra Data NS24 18-Aug-04 5,185 Cidra Data NS13 18-Aug-04 5,175 Cidra Data NS06 20-Aug-04 5,165 Cidra Data NS16 21-Aug-04 5,152 Cidra Data NS22 21-Aug-04 5,147 Cidra Data NS21 21-Aug-04 5,154 Cidra Data 6 Well Date Extrapolated Pressure at -11,100' TVDss Datum, psia Data Source NS24 16-Sep-04 5,186 Cidra Data NS14 17-Sep-04 5,172 Cidra Data NS13 13-Oct-04 5,169 Cidra Data NS21 3-Nov-04 5,149 Cidra Data NS22 3-Nov-04 5,132 Cidra Data NS24 19-Dec-04 5,173 Cidra Data NS14 20-Dec-04 5,164 Cidra Data These pressures are graphically represented in the next figure that is a plot of pressure by well versus time. These data indicate pressures dropped slightly during 2004 due to less than balanced voidage make-up. It should be noted that most of these pressures are derived from permanent downhole sensors that are located +/- 500’ TVD above the reservoir pressure datum of -11,100’ TVDss. As such, the reported pressures are extrapolated using an oil gradient. As water cuts increase in some of the wells on the edge of the reservoir, an alternate mean s of extrapolating may be needed. This is under investigation. The extrapolated reservoir pressures for edge wells such as NS21 and NS22 could be as much as 125 psi higher than currently reported. A complete listing of data from these surveys is shown i n Attachment 4 on the AOGCC Reservoir Pressure Report form. 7 Northstar Reservoir Pressure by Well 5080 5100 5120 5140 5160 5180 5200 5220 5240 Jan-02Feb-02Mar-02Apr-02May-02Jun-02Jul-02Aug-02Sep-02Oct-02Nov-02Dec-02Jan-03Feb-03Mar-03Apr-03May-03Jun-03Jul-03Aug-03Sep-03Oct-03Nov-03Dec-03Jan-04Feb-04Mar-04Apr-04May-04Jun-04Jul-04Aug-04Sep-04Oct-04Nov-04Dec-04Pressure, psiaNS06 NS07 NS08 NS09 NS12 NS13 NS14 NS15 NS16 NS17 NS18 NS19 NS20 NS22 NS21 NS23 NS24 NS25 NS27 NS29 NS31 8 D) Results and Analysis of Production and Injection Log surveys, tracer surveys, observation well surveys and any other special monitoring. One injection profile and three production profiles were obtained in 2004. The following table summarized these as well as previous profile results. Well Name Well Type Date Type Shublik D Ivishak Zone E Ivishak Zone D Ivishak Zone C3 Ivishak Zone C2 Ivishak Zone C1 Ivishak Zone B NS23 Injector 7/13/2003 Memory S/T/P 6 29 13 18 16 18 NS27 Injector 7/21/2004 S/T/P 5 12 19 26 38 NS13 Producer 10/4/2004 S/T/P/Grad/Ghost/DEFT 12 59 19 10 NS08 Producer 12/7/2004 S/T/P/Gradio/Ghost 55 31 9 5 NS09 Producer 12/11/2004 S/T/P/Gradio 54 29 17 0 Percentage of flow from/to interval. Blank intervals are not perforated. Leak detection logs were run on NS31 and NS08 to find the source of T x IA communication. A suspected leak at the packer was confirmed in NS31. A RWO was conducted in early 2005 to correct this problem. A tubing connection leak was identified in NS08. A patch was set across this leak in early 2005. A tracer study was initiated in 2004. Unique chemical tracers were injected into the six Northstar gas injection wells (NS17, NS23, NS25, NS27, NS29 and NS31) on April 12, 2004. Gas samples are taken from each producer once every two weeks. Results to date show NS29 is supporting several of the central wells (NS07, NS08, NS13 and NS16), NS17 has broken through to NS18 and NS23 has broken through to NS08. The attached plots show wells that have seen tracer so far. 9 Tracer Response to NS29 0 0.1 0.2 0.3 0.4 0.5 0.6 0 50 100 150 200 250 Days After InjectionTracer Conc. (ppb v/v)NS07 NS08 NS13 NS16 10 Tracer Response to NS17 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0 50 100 150 200 250 Days After injectionTracer Conc. (ppb v/v)NS18 11 Tracer Response to NS23 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0 50 100 150 200 250 Days After InjectionTracer Conc. (ppb)NS08 12 E) Review of pool production allocation factors and issues over the prior year Theoretical production is calculated for each Northstar producing well on a daily basis. A well’s theoretical production is calculated using average wellhead flowing pressure and hours on production as follows: ltheoreticaaof n whsi whfproduced QQP Phours =´÷÷ ø ö çç è æ ÷÷ ø ö çç è æ-´124 Where: hours produced = hours on line Pwhf = average wellhead flowing pressure Pwhsi = shut-in wellhead pressure n = flow exponent Qaof = absolute open flow of well with Pwhf = 0 psi Qtheoretical = theoretical production The input parameters (n, Qaof and Pwhsi ) for each well are determined from well test data and systems analys is and are reviewed each time new test data becomes available. The actual total production for a day is divided by the summation of the theoretical production from each well to calculate a daily allocation factor. This allocation factor is then multiplied by each well’s theoretical production to calculate allocated production. Allocation factors for 2004 had an average value of 1.059 and a median of 1.065. 13 F) Review of Annual Plan of Operations and Development and Future Development Plans Northstar concluded 200 4 with six injection wells (NS17, NS23, NS25, NS27, NS29 and NS31), fifteen producing wells (NS06, NS07, NS08, NS09, NS12, NS13, NS14, NS15, NS16, NS18, NS19, NS20, NS21, NS22, and NS24) and two Class I disposal wells (NS10 and NS32) on line. During 2004, the NS25 injector, the NS16 and NS21 producers and NS32 disposal well were brought on line. NS16 is unique in that it was drilled, completed, and perforated in 2003 but not brought on line until 2004 because of an ice plug in the tubing. This ice plug was removed with coiled tubing and the well was brought on line in 2004. This drilling activity is summarized in the following table. 14 Northstar - Year End Wells Year Count Producers Injectors Class I Disposal 1 NS07 NS27 NS10 2 NS08 NS29 3 NS09 NS31 4 NS13 5 NS14 2002 6 NS15 1 NS07 NS27 NS10 2 NS08 NS29 3 NS09 NS31 4 NS13 NS17 5 NS14 NS23 6 NS15 7 NS24 8 NS18 9 NS22 10 NS06 11 NS12 12 NS19 2003 13 NS20 1 NS07 NS27 NS10 2 NS08 NS29 NS32 3 NS09 NS31 4 NS13 NS17 5 NS14 NS23 6 NS15 NS25 7 NS24 8 NS18 9 NS22 10 NS06 11 NS12 12 NS19 13 NS20 14 NS16 2004 15 NS21 MMS wells in bold 15 Future Development Plans We recognize the possibility that satellite hydrocarbon accumulations may exist within expected drilling reach from the island. These targets will be the subject of additional appraisal. Infill wells and or sidetracks to optimize recovery f rom the Northstar pool are also possible. As of March 2005, two additional infill development wells are planned. Drilling is ongoing on the first well (NS05) and a second well (NS28) is scheduled. 16 G) Status of Wells Shut-in for 365 days or More (20 AAC 25.115) There were no wells shut-in for all of 2004. 17 Attachment 1: MAP OF NORTHSTAR WELL LOCATIONS Well Status 12/31/04 Bottomhole Locations 0 Abandoned 3 Disposal Well *Gas injector )Not Complete )Oil Producer Ivishak Boundary Lease Boundary Unit Boundary Township / Range Boundary Northstar Well Status for AOGCC Annual Performance Report E. M. Fueg 3/9/05 Projection Information Alaska State Plane Zone 4 Clarke 1866, NAD 1927R13ER12E R14ER14ET14N T13N R13ER13ER12ER13ER13ER14ER13E) ) ) ) ) 3 ))) ) ) * ) ) ) ) ) * ) * 0 * ) * * 3 ADL312799 Y0179 ADL312798 ADL312808 Y1645 Y0181 ADL312809 ADL355001 NS13 NS26 NS15 NS05 NS06 NS07 NS08 NS09 NS10 NS12NS14 NS16 NS17 NS18 NS19 NS20 NS21 NS22 NS23 NS24 NS25 NS27 NS28 NS29 NS31 NS32 bp LEGEND TR A N S - A L A S K A P I P E L I N E 32 MILES 10 18 Attachment 2 NORTHSTAR FIELD 2004 OVERVIEW STATISTICAL SUMMARY WELL STATISTICS 2004 (12/31/04) Producers 15 Injectors 6 NOTES: (1) Well count data reflects ONLY those wells which contributed to production/injection during the respective year PRODUCTION/INJECTION STATISTICS Production 2004 Cumulative: Start-Up through 12/31/04 Oil (BBL) 25,078,477 67,215,375 Gas (MCF) 104,382,882 225,546,155 Water (BBL) 2,817,059 3,870,835 Injection Water (BBL) into NS10 & NS32Disposal Well 3,029,981 5,632,055 Gas (MCF) 131,501,283 300,862,589 Balance Cum Production (MRB) 90,082 203,937 Cum Injection (MRB) 89,421 203,633 Over/Under (MRB) -661 -304 AVERAGE RATE DATA 2004 Production Oil, BOPD 68,520 Gas, MCF/D 285,199 Water, BWPD 7,697 Injection Water, BWPD into NS10 & NS32Disposal Well 8,279 Gas, MCFPD 359,293 AVERAGE RESERVOIR PRESSURE at -11,100’ TVDss Average of surveys obtained in 2004, psia 5,179 Note: Average Rate Calculations based on 366 days in 2004 19 Attachment 3 Corrected 2003 Voidage Balance by Month of Produced Fluid and Injected Fluids Month Oil, MRB Free Gas, MRB Water, MRB Total Voidage, MRB 2003 Cum, MRB Cum since start-up, MRB Formation Gas, MRB Import Gas, MRB Total Injection, MRB 2003 Cum, MRB Cum since start-up, MRB Net Injection, MRB 2003 Cum, MRB Cum since start-up, MRB January-03 3,335 1,394 27 4,755 4,755 52,932 3,631 1,576 5,207 5,207 50,557 451 451 -2,375 February-03 4,386 1,237 59 5,682 10,437 58,614 4,191 1,218 5,409 10,615 55,965 -273 178 -2,649 March-03 4,306 1,837 89 6,232 16,670 64,846 4,719 1,701 6,421 17,036 62,386 188 366 -2,460 April-03 2,985 1,156 52 4,193 20,862 69,039 3,134 1,784 4,918 21,954 67,304 725 1,092 -1,735 May-03 4,553 1,422 76 6,051 26,914 75,090 4,469 1,062 5,531 27,485 72,834 -521 571 -2,256 June-03 4,715 1,656 71 6,442 33,355 81,532 4,828 1,671 6,500 33,984 79,334 58 629 -2,197 July-03 4,200 1,570 64 5,834 39,190 87,366 4,371 1,696 6,067 40,051 85,401 233 862 -1,965 August-03 4,194 1,125 70 5,388 44,578 92,754 3,936 1,829 5,765 45,816 91,166 377 1,239 -1,588 September-03 4,546 0 95 4,640 49,218 97,395 2,984 2,020 5,004 50,821 96,171 364 1,603 -1,224 October-03 5,119 936 118 6,172 55,390 103,567 4,384 2,167 6,551 57,371 102,721 378 1,981 -846 November-03 4,201 901 119 5,221 60,612 108,789 3,728 1,944 5,672 63,043 108,393 450 2,431 -396 December-03 4,030 934 102 5,067 65,678 113,855 3,645 2,174 5,819 68,862 114,212 753 3,184 357 2003 Totals 50,569 14,168 942 65,678 48,020 20,842 68,862 3,184 Produced Fluids Injected Fluids Net Injection (Injection - Production)