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Home My WebLink About2015 Schrader Bluff Oil PoolPage | i Eni Petroleum – Alaska Development 2015 Annual Reservoir Surveillance Report Schrader Bluff Pool Nikaitchuq Field Page | ii Eni Petroleum – Alaska Development Table of Contents 1. 2015 Development Activity Summary .................................................................................................. 3 2. Reservoir Pressure Surveys at the Nikaitchuq Schrader Bluff Pool ...................................................... 6 3. Pool Allocation Factors and Issues over the Year 2015 ...................................................................... 10 4. Reservoir Management Summary ...................................................................................................... 11 4.1 2015 Fall PFO and DTS Data Acquisition Campaign ........................................................................... 12 4.2 Voidage Balance by Month of Produced Fluids and Injected Fluids on a Standard and Reservoir Volume Basis with Yearly and Cumulative Volumes ................................................................................... 14 Nikaitchuq Field ‐ Drilling Schedule as at December 2015 ......................................................................... 16 Page | 3 Eni Petroleum – Alaska Development 1. 2015 Development Activity Summary For the year 2015, the development activities were focused on drilling new wells from Spy Island. A total of ten (10) new wells were added to the current well inventory as follows: 4 oil producers, 4 Dual lateral oil producers and 2 injector wells (See Table 1 and Figure 1 below). In addition, well intervention/workover activities were conducted for five wells to maintain the production field performance (See Table 2, below). Well Name Well Type Placement Date Drilling Path SP31‐W7 Oil Producer 2/1/2015 Spy Island SP31‐W7 L1 Dual lateral Oil Producer 2/18/2015 Spy Island SI34‐W6 Water Injector 3/31/2015 Spy Island SP04‐SE5 Oil Producer 4/25/2015 Spy Island SP04‐SE5 L1 Dual lateral Oil Producer 5/16/2015 Spy Island SI07‐SE4 Water Injector 6/13/2015 Spy Island SP01‐SE7 Oil Producer 7/8/2015 Spy Island SP01‐SE7 L1 Dual lateral Oil Producer 7/28/2015 Spy Island SP28‐NW3 Oil Producer 9/15/2015 Spy Island SP28‐NW3 L1 Dual lateral Oil Producer 10/16/2015 Spy Island Table 1.2015 Well Placement summary Schedule for Nikaitchuq Field Well Name Well Type WO Completion Date Drilling Path OP23‐ WW02 Water Well 4/2/2015 Oliktok Point OP22‐ WW03 Water Well 4/13/2015 Oliktok Point OP16‐03 Oil Producer 7/22/2015 Oliktok Point OP04‐07 Oil Producer 8/4/2015 Oliktok Point OP26‐ DSP02 Disposal Well 10/14/2015 Oliktok Point Table 2. 2015 ESP replacement workover job summary for Nikaitchuq Field Page | 4 Eni Petroleum – Alaska Development Figure 1. Nikaitchuq development Map showing the completed well paths and its reservoir units up to Dec 2015. Green = producer, Blue = injector, Yellow = Dual lateral producer, Purple = N Sand Appraisal well. SI11-FN6 SI13-FN4 SI14-N6 SI17-SE2 SI19-FN2 SI20-N4 SI25-N2 SI26-NW2 SI29-S2 SI32-W2 SI34-W6 SI35-W4 SP05-FN7 SP08-N7 SP10-FN5 SP12-SE3 SP16-FN3 SP18-N5 SP21-NW1 SP22-FN1 SP23-N3 SP24-SE1 SP27-N1 SP30-W1 SP31-W7 SP33-W3 SP36-W5 OI06-05 OI07-04 OI11-01 OI13-03 OI15-S4 OI20-07 OI24-08 OP03-P05 OP04-07 OP05-06 OP08-04 OP10-09 OP12-01 OP14-S3 OP16-03 OP17-02 OP18-08 OP19-T1N SI07-SE4 OP09-S1 OP-I2 SP04-SE5 Spy Island Oliktok Point SI02-SE6 (P3) SP01-SE7 SI06-FN8 (P2) SP03-FN9 (P2) SP28-NW3 490000 491000 492000 493000 494000 495000 496000 497000 498000 499000 500000 501000 502000 503000 504000 505000 506000 507000 508000 509000 510000 511000 512000 513000 514000 515000 516000 517000 518000 519000 520000 521000 522000 523000 524000 490000 491000 492000 493000 494000 495000 496000 497000 498000 499000 500000 501000 502000 503000 504000 505000 506000 507000 508000 509000 510000 511000 512000 513000 514000 515000 516000 517000 518000 519000 520000 521000 522000 523000 5240006036000603800060400006042000604400060460006048000605000060520006054000605600060580006060000606200060640006066000606800060700006072000607400060360006038000604000060420006044000604600060480006050000605200060540006056000605800060600006062000606400060660006068000607000060720006074000 0 2000 4000 6000 8000ftUS 1:21000 Nikaitchuk Development Date 03/01/2016 Signature Alaska Dev. Team Nikaitchuq Development Pattern - December 2015 Page | 5 Eni Petroleum – Alaska Development The well plan activity in 2009 had a total well count of 51. The well pattern and summary of the activity to the end of 2015 was 55 wells (not including the dual lateral well paths) and is summarized in Table 3 as below: Planned Activity (2009) Activity up to date (December 2015) OPP SID Total OPP SID Total Well Type Injector 8 12 20 8 13 21 Producer 11 15 26 11 18 29 Disposal 1 1 2 1 1 2 Water Source 3 0 3 3 0 3 Total 23 28 51 23 32 55 Dual Lateral Well Paths 8 9 17 OPP = Oliktok point development path (onshore) SID = Spy Island Development path (offshore) Table 3. Total planned well count for Nikaitchuq Development Oil production at Nikaitchuq field has responded positively to waterflood. The positive waterflood response to date indicates that waterflood technology chosen as the main oil recovery strategy for this field continues to be working well. Figure 2 below shows Nikaitchuq field’s oil production and water injection history from January 2013 through December 2015. The drop in injection during 1Q15 is due to a water source wells ESP failure and is discussed in subsequent sections. Page | 6 Eni Petroleum – Alaska Development Figure 2. Nikaitchuq Field production and events summary 2013‐2015 2. Reservoir Pressure Surveys at the Nikaitchuq Schrader Bluff Pool Similar to previous years reservoir pressure monitoring activities, during 2015 reservoir pressures were monitored by controlling intake BHPs as shown in Figures 2a & 2b for OPP and SID, respectively. These plots show how intake pressures have been gradually stepped down while monitoring signs of sand production, rising watercuts (WC) and gas‐oil ratios (GOR) and balancing voidage across all sectors in the field. The spread in SID in 2015 reflects ESP lift capacity saturation as wells have responded to injection as shown in Figures 2c & 2d for OPP and SID respectively. Reservoir pressures were measured in new wells prior to placing them in service in 2015. Also, planned and unplanned downtime opportunities in 2015 made it possible to measure reservoir pressures during pressure fall off (PFO) and distributed temperature surveys (DTS) campaigns. The reservoir pressure measurements in the foregoing campaigns were used to support the Nikaitchuq reservoir model pressure map of 2015 shown in Figure 3. Page | 7 Eni Petroleum – Alaska Development Figure 2a. Intake BHP measurements in year 2015 for active wells at OPP Figure 2b. Intake BHP measurements in year 2015 for active wells at SID Page | 8 Eni Petroleum – Alaska Development On the injector side, wellhead pressures have been capped at an equivalent of 0.60 psi/ft. to avoid injection at pressures that can fracture the reservoir. Figure 2c. Wellhead pressure measurements in year 2015 for injectors at OPP Figure 2d. Wellhead pressure measurements in year 2015 for injectors at SID Page | 9 Eni Petroleum – Alaska Development Injection deficit, due to an ESP failure on a source water well, is reflected in the declining THPs of the first quarter. Starting April, after the workover on the source well, injection THPs are stabilized. Figure 3. Pressure map of Nikaitchuq Field for 2015 Oliktok Point SP05-FN7 SP10-FN5 SP30-W1 SI26-NW2 OI06-05 OI07-04 OI11-01 OI13-03 OI15-S4 OI24-08 OP03-P05 OP04-07 OP OP08-04 OP09-S1 OP10-09 OP12-01 OP14-S3 OP16-03 OP17-02 OP18-08 OP21-WW1 SI20-N4 SI25-N2 SI29-S2 SP18-N5 SP23-N3 SP27-N1 Spy Island OI20-07 OP-I2 SI11-FN6 SI17-SE2 SI19-FN2 SI32-W2 SI35-W4 SP08-N7 SP12-SE3 SP16-FN3 SP21-NW1 SP22-FN1 SP24-SE1 SP33-W3 SP36-W5 SI14-N6 SI13-FN4 SI34-W6 SP SP31-W7 SP28-NW3 SI07-S 490000 492000 494000 496000 498000 500000 502000 504000 506000 508000 510000 512000 514000 516000 518000 520000 490000 492000 494000 496000 498000 500000 502000 504000 506000 508000 510000 512000 514000 516000 518000 520000603500060375006040000604250060450006047500605000060525006055000605750060600006062500606500060675006070000607250060750006077500 603500060375006040000604250060450006047500605000060525006055000605750060600006062500606500060675006070000607250060750006077500200 40060080010001200 1400 1600180020002200 Pressure [psi] qp( ) Page | 10 Eni Petroleum – Alaska Development 3. Pool Allocation Factors and Issues over the Year 2015 Production from all wells producing from the Schrader Bluff pool is commingled at the surface into a common production line. Theoretical production for individual wells from the pool is calculated on a daily basis by using well test allocation. Wells are tested, at least, twice per month for a total of 24 times per year per well. During 2015, 1,065 welltests were performed. Measurements are performed on a multiphase meter. Daily theoretical production for a well was calculated using the last valid well test and the amount of time a well was on production for a given day. For example, if there was a valid well test on the first of the month and another on the fifth of the month, the allocation factor for that well would be calculated on the first through the fourth of the month using the test on the first of the month. Subsequently, the allocation factor will be recalculated on the fifth of the month using the new valid test measured on the fifth. On the monthly level, our AVOCET Manager Production software sums up the allocated volumes from each time period between valid well tests. (Minutes on production/1440 minutes/day)*Daily Rate (stb/d) well test=Theoretical Daily Production The daily allocation factor for the field is calculated by dividing the actual total production for the day by the sum of the theoretical daily production for each individual well. Daily allocated production is assigned to each well by multiplying its theoretical daily production by the daily allocation factor. January 1.0602 February 1.0463 March 1.0529 April 1.0708 May 1.0771 June 1.0681 July 1.0927 August 1.0730 September 1.0971 October 1.1154 November 1.1049 December 1.1066 Figure 4. Average field allocation factor trend for 2015 Page | 11 Eni Petroleum – Alaska Development The average allocation factor for 2015 has been 1.08. During 2015 the allocation factor has crept up, due mainly to the associated back pressure increase on the meter in the test header loop as production volumes increased. Shown in Figure 4 above. 4. Reservoir Management Summary The Nikaitchuq OA reservoir development has focused on two major areas; replenishing reservoir energy by replacing the voidage created by fluid production with water injection, (productivity improvement through workover activities) and adding a second lateral to wells with single laterals. Reservoir energy is monitored by monitoring surface and bottom‐hole pressures. In addition to surface meters measuring tubing pressures, Nikaitchuq oil producers are equipped with downhole gauges which allow real‐time bottom‐hole pressures to be monitored. Additionally, Resman tracer system pairs (oil and water tracers) are deployed in two OPP producers (OP17‐02 & OP05‐06) and six SID producers (SP10‐FN5, SP16‐FN3, SP21‐NW1, SP31‐ W7, SP33‐W3, SP36‐W5), to help assess oil flow distribution along the wellbores and determine locations of water production. Only SP21‐NW1 and SP31‐W7 retain useful life. Eight injector wells (Figure 5), four in Spy Island (SI11‐FN6, SI19‐FN2, SI13‐FN4, SI25‐N2) and four in Oliktok Point (OI11‐01, OP‐I2, OI13‐03, OI24‐08) have been also treated with unique Tracerco tracers in order to evaluate the water flow patterns, the breakthrough time and the sweep efficiency of the water injection. Three OPP injectors (OI06‐05, OI07‐04 & OI11‐01) and two SID injectors (SI14‐N6 & SI20‐N4) are equipped with DTS fiber optics which determines the level of injectivity along the horizontal injection intervals of the injectors. Figure 5 below, shows the Nikaitchuq field map with Resman, Tracerco tracers and the wells injector with DTS fiber optic. Page | 12 Eni Petroleum – Alaska Development Figure 5. Nikaitchuq map showing wells with Resman tracers and DTS Fibers 4.1 2015 Fall PFO and DTS Data Acquisition Campaign Pressure and temperature data acquisition campaigns were conducted during the 2015 fall‐off acquisition. During these campaigns, pressure fall‐off (PFO) data collected. The Table 4 below summarized the acquisition dates for injector wells with DTS fiber optic installed. A second opportunity to acquire shut‐in reservoir pressures was during a planned shutdown in August 2015. With the exception of SI32‐W2 which had a longer PFO duration due to the earlier Page | 13 Eni Petroleum – Alaska Development shut in for anti‐collision concerns while drilling nearby SP28‐NW3, the rest of the PFOs happened for approximately 37 hours from 08/21/2015 at 05:30:00 to 08/22/2015 at 18:30:00. Well PFO Start & End Dates Duration WH Pressure (PSI) Injector Start End Hours Start End OI11‐01 03/19/2015 03/21/2015 96 139.2 0 OI07‐04 03/11/2015 03/14/2015 72 225.1 0 OI06‐05 03/11/2015 03/14/2015 72 287.0 203.0 SI14‐N6 03/14/2015 03/19/2015 108 348.5 106.3 SI20‐N4 03/11/2015 03/14/2015 72 208.5 79.8 Table 4.PFO/DTS Survey Date and Time during Fall 2015 Campaign A DTS analysis, based on temperature profiles was performed for OI11‐01. The DTS acquisition has been carried out in March 2015 (Qi≈2,625 bbls/d) during the periodical Fall‐off activity (Figure 6 below) executed on the well. Figure 6. Rate&Tubing pressure plot from June 2014 to April 2015, and FO periods acquired by DTS The analysis has been focused on the detection of the possible differences from previous situation by means of a time lapse analysis. The preferential injectivity behaviour, already found in previous interpretations (2014), is still present and it could be mainly located at the heel and especially at the toe of the well. However, the comparison highlights that in March 2015 the injection profile reached a more balanced shape than before. This effect is due to an increase of injectivity in the middle zone of the reservoir, providing a more homogeneous distribution of the overall injection profile (Figure 6). Page | 14 Eni Petroleum – Alaska Development Figure 7. OI11‐01 Inflow zones contributions from 2015 DTS Transient model 4.2 Voidage Balance by Month of Produced Fluids and Injected Fluids on a Standard and Reservoir Volume Basis with Yearly and Cumulative Volumes A total of approximately 9.0 million barrels of oil was produced from the Nikaitchuq field during the year 2015 at an average daily production of 24700 bopd. Injected volumes of water during year 2014 were about 12.3 million barrels at an average daily rate of 33600 bwpd. During the first three months of the year there was an injection deficit, due to a source water well ESP failure, which is normalized starting April. Table 5 below summarizes the entire voidage replacement for the Nikaitchuq field in 2015. The spikes in the graph are typically associated with Alyeska proration days. Page | 15 Eni Petroleum – Alaska Development Monthly Subsurface Production Voidage Monthly Subsurface Injection Voidage Voidage Replacement Ratio Oil Water Total Water Injection Monthly Jan‐15 802 210 1012 784 0.78 Feb‐15 732 191 923 705 0.76 Mar‐15 823 218 1040 658 0.63 Apr‐15 759 221 980 907 0.93 May‐15 724 233 957 1088 1.14 Jun‐15 731 249 980 1098 1.12 Jul‐15 798 288 1085 1165 1.07 Aug‐15 753 310 1063 1100 1.04 Sep‐15 810 332 1142 1154 1.01 Oct‐15 840 374 1213 1218 1.00 Nov‐15 816 363 1180 1190 1.01 Dec‐15 833 370 1203 1216 1.01 Table 5.2014 Nikaitchuq field monthly production/injection volumes and voidage replacement ratios 0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 1‐Jan‐15 1‐Feb‐15 1‐Mar‐15 1‐Apr‐15 1‐May‐15 1‐Jun‐15 1‐Jul‐15 1‐Aug‐15 1‐Sep‐15 1‐Oct‐15 1‐Nov‐15 1‐Dec‐15 Page | 16 Eni Petroleum – Alaska Development Nikaitchuq Field ‐ Drilling Schedule as at December 2015