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Home My WebLink About1988 Mid Year Endicott Oil PoolStandard Alaska Production Company 900 East Benson Bwlevard P.O. Bo. 196612 Anchorage, Alaska 995196612 19071 5615111 09 June 24, 1988 C. V. Chatterton, Chairman Alaska Oil and Gas Conservation Commission 3001 Porcupine Drive Anchorage, Alaska 99501 Dear Mr. Chatterton: RE: 1988 Mid -Year Endicott Oil Pool - Waterflood Pilot Surveillance Report Attached is our first semi-annual Endicott Waterflood Pilot Surveillance Report. This report covers the status of the waterflood pilot from the initiation of injection in February, 1988 through May, 1988. In addition, field surveillance and material balance information is provided from field start-up in October, 1987 through May, 1988. If you need additional information, please contact Mr. Gary Adamson at 564-4624. JWB/GA:slb cc: Working Interest Owners A vnn of the o.gmai Smodard Oil Company FounOhlc, n 1970. Sincerely, J. W. Buckee Vice President, Development Planning WATERFLOOD PILOT SURVEILLANCE REPORT ENDICOTT OIL POOL JUNE, 1988 - Project Status Summary This report covers the period from the start of water injection (February 29, 1988) through May 31, 1988 for the Endicott Oil Pool. During the report period, water injection was started in three wells. The objective of this pilot is to determine reservoir injectivity and potential waterflood operating problems. Exhibit 1 shows a map of the field with the current wells including the existing water injectors. Cumulative water injection into the Endicott Oil Pool from pilot start-up through May 1988 is 771 MSTB as detailed in Exhibit 2. Cumulative production since start-up is 25.1 MMSTB oil, 22.8 BSCF gas, and 1.0 MMSTB water. The cumulative injected and produced volumes since start-up by major sub -zone (sand) on a reservoir volume basis are shown in Exhibit 3. The volumes shown in Exhibit 3 do not include production from sub -zones 3B and 3C as injection has not been started in these intervals. As of May 30, 1988, reservoir voidage exceeded gas and water injection by 20.4 MMRB. Graphs of injection rates and wellhead pressure vs. time for the 3 active injection water wells are presented in Exhibit 4. Pressure surveys taken over the past few months have shown that the field is effectively divided in two by a fault system that runs east -west through the middle of the field. Coincidentally, with one exception, the wells to the northwest of this fault system are those drilled from the Main Production Island (MPI) while those to the southeast were drilled from the Satellite Drilling Island (SDI). Observed pressures in the SDI region are 150 to 300 psi lower than those observed in the MPI region due to lack of communication with gas reinjection in the MPI area and the fact that there is very little gas cap volume in the SDI area. Based on this observed information, the areas on each side of the fault system are being treated as separate reservoirs. The bottomhole pressure data obtained since start-up are summarized in Exhibit 5. Water injection was initiated into the Endicott Oil Pool in well 5-02/Sag 10 on February 28, 1988. This well is located in the MPI region in the 2A sub - zone. Injectivity (II) rapidly fell from an initial value of 13 BPD/psi to only 4 BPD/psi in only 10 days. The well was stimulated with acid and its II increased to 10 BPD/psi but again fell to 5 BPD after 5 days. The well was stimulated with acid again on April 8. At the same time, a program of oxygen scavenger treatment to supplement the gas stripping deoxygenation tower was started for the sea water. Tests had shown that the solids content in the water had a high concentration of iron, felt to be due to corrosion products. After the acid stimulation, the well's II increased to 8 BPD/psi and has remained fairly constant since that time. Injection started in well 1-37/P-24 on March 10, 1988. This well is located in the MPI region in the 2B sub -zone. The initial injectivity of 11 BPD/psi fell rapidly to 5 BPD/psi in five days. The II remained fairly constant until a step rate test was performed on April 25-27. After the the well was fractured during the test, the II increased to 10 BPD/psi and then slowly declined to 7 BPD/psi where it has remained fairly constant, even though injection has been kept below the fracture gradient. The plugging material in the perforations was probably pushed into the fractures created during the step rate test, effectively stimulating the well. The program of oxygen scavenger has minimized re -damaging of the well. As mentioned earlier, a step rate test conducted on well 1-37/P-24 on April 25-27. The objective of this test was to determine the fracture gradient for the Endicott formation and estimate the size of the fractures created. The results of the test indicated that the fracture pressure is approximately 0.57 psi/ft, although some deviation from radial flow was noted as low as 0.54 psi/ft. Calculated effective fracture lengths were estimated to range from 2 to 64 ft, depending on assumptions. Even the longest estimated fracture length would not impact waterflood recovery. Temperature logs showed that the fracture did not grow vertically out of zone. A third well, 4-02/0-28 was placed on injection in the SDI region of the field. Initial injection was into the tar layer in sub -zone 2B to test its injectivity. Initial injectivity was low (3.5 BPD/psi) and declined to virtually nothing in five days, in spite of injection pressures above the fracture gradient. The injectivity decline was probably due to solids plugging and super charging of the low permeability tar layer. The initial water quality was poor (28 ppm tss) due to contamination from residue in the long injection line from the MPI to the SDI. After injection ceased into the tar interval, additional perforations were opened up in the 2A sub -zone aquifer below the tar. Initial injectivity was low (less than 1 BPD/psi) but rapidly improved to over 12 BPD/psi as the well cleaned up while injecting above the fracture pressure. Injectivity has remained high as injection pressures were slowly lowered below the nominal 0.57 psi/ft fracture gradient. Pressure surveys taken in well Q-28 showed that the tar layer and aquifer below the tar layer had minimal communication with the reservoir above the tar. While a pressure drop of 450 psi has been observed above the tar in sub - zones 2A and 2B, the pressure drop observed in and below the tar was only about 50 psi. Thus, injection in or below the tar will probably not be very effective for pressure maintenance in the oil zone. Additional perforations will be added soon to this well in the 3A sub -zone aquifer above the tar layer. The additional flushing of the injection line has improved water quality to less than 5 ppm tss. The 3A sub -zone is the primary target for this well. At this time, there has been no observed production response to water injection, as expected. Production in the wells nearest to the water injectors is being monitored for any indication of waterflood response. The lack of observed response is good and indicates that there should not be any severe communication problems. Surveillance and diagnostic logs which have been obtained since start-up are summarized in Exhibit 6. Future plans call for drilling or converting two wells for injection in each major sub -zone (2A, 2B and 3A) on each side of the dividing fault system. Due to the significant pressure drop observed in the SDI region of the field, full scale waterflood plans for that region have been accelerated and should be in place by the end of 1988. Full scale waterflood for the MPI region of the field will not be implemented until 1989 to allow for more performance observation before finalizing those plans. Pressure support from the gas cap and gas re-injection are keeping pressures in this region higher and allow for more study time before implementing a full field waterflood. A radioactive tracer program will be initiated in July to aid the waterflood pilot surveillance efforts. n M C� v q O I M � M M I M� OAS � M N N I V � � A , �z as O N,------------- o �N \ z � N w N p •=� d N CIA N I Y \l�J� It Nd N pw N N H P. O � N IT o W T I Z W P. O I o W T I Z W W z z I Q Q I — I I �� I � I EXHIBIT 2 ENDICOTT OIL POOL SUMMARY OF PERTINENT DATA (as of May 31, 1988) Water Injection Start -Up: February 28, 1988 Endicott Production Since Field Start -Up: Oil (MSTB) 25,160 Gas (MMSCF) 22,817 Water (MSTB) 1,030 Endicott Injection Since Field Start -Up: Gas (MMSCF) 17,696 Water (MSTB) 771* Wells in Operation: Production 30 Gas Injection 3 Water Injection 3 Produced Water Disposal I * Water injection volumes do not include Cretaceous injection or injection in or below the tar in the Endicott Pool. Produced Fluids (MRB) Oil Free Gas Water Total Injected Fluids (MRB) Water Gas Total Net Volumes = Total Produced Fluids (MRB) Oil Free Gas Water Total Injected Fluids (MRB) EXHIBIT 3 ENDICOTT OIL POOL RESERVOIR BALANCE - WATERFLOOD SANDS EFFECTIVE PRODUCTION SINCE FIELD START-UP (October 1987 - May, 1988) MPI Region 3A Sand 2B Sand 2A Sand MPI Total 3734.0 6806.4 9103.0 19,643.4 616.2 0 0 616.2 31.8 44.5 135.7 212.0 4382.0 6850.9 9238.7 20,471.6 0.0 391.7 395.8 787.5 0.0 146.3 6529.5 4826.3 11,502.1 0.0 146.3 6921.2 5222.1 12,289.6 0.0 ection-Production (MRB) 0.0 12,209.7 -4235.7 70.3 -4016.6 -8182.0 Total SDI Region -5249.5 -2249.3 -12,209.7 3A Sand 2B Sand 2A Sand SDI Total FIELD TOTAL 3885.6 4940.9 2214.4 11,040.9 30,684.3 388.9 35.3 3.8 428.0 1,044.2 436.4 273.3 31.1 740.8 952.8 4710.9 5249.5 2249.3 12,209.7 32,681.3 Water 0.0 0.0* 0.0* 0.0 787.5 Gas 0.0 0.0 0.0 0.0 11,502.1 Total 0.0 0.0 0.0 0.0 12,209.7 Net Volumes = Injection -Production (MRB) Total -4710.9 -5249.5 -2249.3 -12,209.7 -20,391.7 * Excludes water injected into and below the tar layer or injected into the Cretaceous reservoir down the annulus of 1-37 and 4-02. EXHIBIT 4 ENDICOTT PILOT INJECTION WELLS INJECTION RATE AND WELL HEAD PRESSURE TIME (START-UP - JUNE 15, 1988) 0 Alaska Oil & Ct r ' , C ::misstun VISJ — 'SS38d ad3H T3M 0 0 0 0 0 0 o a 00 t0 d N O e •. .. is W 01j: p W C � cc ...... 3 J, Z '.• n ui • 'w. MD ..... ' aw `� H Z•:... o a N p IL :. a h M ,ti r A. ....�..... r.M j ulir ...`. p w ,> U W Er 0dM8W - 31t/a N01103MI juL 15 128a —j Alaska Oil & Ct r ' , C ::misstun Fco :c,, dlSd — 'SS38d (IV3H 113M 0 0 0 0 0 0 0 0 0 Lo rQ0N 0 0 .�- to O i i : : O r � o � N( PM s Gi 4 R; (� CA x a. ,• Z W ' Z ,- ' Q W � Z N O� . ............................ .......................................... ------. et J � W ........---•-•-• ............................................................ �< N adM6W - 31YU N01103PN1 C h Alaska Oil & C,. ,;fission Alaska Oil & r C^!-.!7is;ioa VISd — 'SS32Jd ad3H 113M O O O O O O O O O O 6 O O O O t♦ n t� Q1 Q 2: tri a' W 2 n 7 + .1 O ' n N uj -_ i N ��w r♦ Q r e a O a. :+• a Ij W _' w t Vm o m CIO a p6W a o iW adM9W - 31H» N01103PN1 R.F C F7" 1 Ee JUL 15 1^88 Alaska Oil & r C^!-.!7is;ioa dlSd - 'SS3�Id ab3H 73M 0 0 0 m o 0 c o 0 0 0 ip 00 0 0 It N O N i i i i i i � o c , • b: C F w ¢ a Z QLLI �•;r v I a LU Z � Q w p Z c N � r J LLI 3 ..................•--......................_............_...............----- co to .. r 7 N C adM9W - SIVU Nouog NI blSd — 'SS3bd ad3H T3M 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 O .t j, n t� i Qi Q Q. W z cc 'f n Z . O � s LLIN .... Z " W Q C7 CO) :"' . . N • LO.a... ..................................' n Q ,3 LLI w x co 06 W O T m tp a N 4dM8W - 31Va NQIIo3PN1 EXHIBIT 5 ENDICOTT OIL POOL BOTTOMHOLE PRESSURE SURVEYS (October, 1987 - May, 1988) 1 PRESSURE READING WELL TEST DATE @ 10000' TVDsS (psia) ---------- 1-05/0-20 ---------- 14 -APR -88 --------------------- 4833 1-09/J-18 01 -OCT -87 4890 02 -FEB -88 4788 1-29/M-25 30 -JAN -88 4767 O1 -APR -88 4790 1-35/0-25 21 -JAN -88 4809 1-37/P-24 07 -JAN -88 4801 1-47/Q-21 17 -DEC -87 4608 1-55/R-25 07 -MAY -88 4790 2-04/M-19 28 -FEB -88 4769 2-06/J-22 30 -MAR -88 4849 2-08/K-16 07 -MAR -88 4789 2-44/R-12 27 -FEB -88 4802 28 -MAR -88 4502 2-52/5-14 25 -OCT -87 4900 27 -JAN -88 4784 2-62/Q-17 05 -FEB -88 4737 3-01/N-29 10-NOV-87 4839 05 -DEC -87 4696 22 -JAN -88 4623 27 -MAR -88 4512 3-05/0-29 06 -DEC -87 4907 30 -MAR -88 4813 26 -MAY -88 4460 3-15/K-33 23 -DEC -87 4836 3-21/L-34 04 -DEC -87 4736 3-23/N-32 03 -DEC -87 4828 3-27/M-33 07 -OCT -87 4892 3-33/K-37 01 -MAR -88 4570 O1 -MAR -88 4467 3-35/L-36 24 -JAN -88 4545 3-47/Q-35 28 -FEB -88 4488 4-02/Q-28 04 -MAY -88 4785 4-06/Q-32 09 -DEC -87 4600 5-01/SG07 27 -MAR -88 4812 1 EXHIBIT 6 ENDICOTT OIL POOL SURVEILLANCE AND DIAGNOSTIC LOGS (October, 1987 - May, 1988) WELL RUN DATE SURVEY TYPE ---------- 1-01/J-19 --------- 14 -MAY -88 ------------------ PRESSURE RFT 1-09/J-18 22-NOV-87 BOTTOM HOLE SAMPLE 1-09/J-18 29 -DEC -87 FLOWMETER 1-09/J-18 10 -JAN -88 TDT 1-09/J-18 14 -JAN -88 TDT 1-09/J-18 24 -MAR -88 PRESSURE PULSE/INT: 1-25/N-22 08 -APR -88 FLOWMETER 1-25/N-22 08 -APR -88 TDT 1-27/P-20 03 -FEB -88 FLOWMETER 1-27/P-20 03 -FEB -88 TEMPERATURE SURVEY 1-27/P-20 29 -FEB -88 TDT 1-27/P-20 09 -MAY -88 NEUTRON 1-29/M-25 31 -JAN -88 FLOWMETER 1-29/M-25 04 -FEB -88 TDT 1-35/0-25 21 -JAN -88 BOTTOM HOLE SAMPLE 1-35/0-25 08 -FEB -88 FLOWMETER 1-35/0-25 08 -FEB -88 TEMPERATURE SURVEY 1-35/0-25 27 -FEB -88 TDT 1-37/P-24 23 -FEB -88 TDT 1-37/P-24 26 -FEB -88 TDT 1-37/P-24 24 -APR -88 FLOWMETER 1-37/P-24 24 -APR -88 TEMPERATURE SURVEY 1-37/P-24 25 -APR -88 PRESSURE STEP RATE 1-37/P-24 30 -APR -88 FLOWMETER 1-37/P-24 30 -APR -88 TEMPERATURE SURVEY 1-37/P-24 02 -MAY -88 TDT 1-41/0-23 29 -JAN -88 FLOWMETER 1-41/0-23 03 -MAR -88 TDT 1-47/0-21 16 -DEC -87 FLOWMETER 2-04/M-19 28 -FEB -88 FLOWMETER 2-04/M-19 28 -FEB -88 TEMPERATURE SURVEY 2-04/M-19 01 -MAR -88 TDT 2-08/K-16 15 -FEB -88 PRESSURE RFT 2-08/K-16 02 -APR -88 FLOWMETER 2-14/0-16 10-NOV-87 FLOWMETER 2-14/0-16 26 -MAR -88 FLOWMETER 2-34/P-14 09 -FEB -88 FLOWMETER 2-34/P-14 09 -FEB -88 TEMPERATURE SURVEY 2-44/R-12 27 -MAR -88 FLOWMETER J Page 2 of Exhibit 6 EXHIBIT 6 ENDICOTT OIL POOL SURVEILLANCE AND DIAGNOSTIC LOGS (October, 1987 - May, 1988) 2-52/S-14 19-NOV-87 BOTTOM HOLE SAMPLE 2-52/S-14 04 -FEB -88 TEMPERATURE SURVEY 2-52/S-14 04 -FEB -88 FLOWMETER 2-62/0-17 31 -JAN -88 FLOWMETER 2-62/0-17 31 -JAN -88 TEMPERATURE SURVEY 2-62/0-17 05 -FEB -88 FLOWMETER 3-01/N-29 05 -DEC -87 FLOWMETER 3-01/N-29 28 -MAR -88 TOT 3-05/0-29 13 -JAN -88 TOT 3-05/0-29 25-14AY-88 FLOWMETER 3-05/0-29 25 -MAY -88 TEMPERATURE SURVEY 3-15/K-33 16 -APR -88 TOT 3-21/L-34 03 -JAN -88 FLOWMETER 3-23/N-32 07 -JAN -88 FLOWMETER 3-27/M-33 17 -JAN -88 FLOWMETER 3-33/K-37 26 -JAN -88 FLOWMETER 3-35/L-36 24 -JAN -88 BOTTOM HOLE SAMPLE 3-35/L-36 30 -JAN -88 FLOWMETER 3-35/L-36 30 -JAN -88 TEMPERATURE SURVEY 3-47/0-35 27 -FEB -88 FLOWMETER 3-47/0-35 27 -FEB -88 TEMPERATURE SURVEY 3-49/J-40 18 -JAN -88 FLOWMETER 3-49/J-40 01 -FEB -88 FLOWMETER 4-06/0-32 08 -DEC -87 FLOWMETER 4-06/0-32 28 -FEB -88 TOT 4-08/P-27 31 -DEC -87 FLOWMETER 4-20/M-35 27 -DEC -87 FLOWMETER 5-01/SGO7 20 -MAR -87 WORKOVER-RIG OTHER 5-01/SGO7 08 -MAR -88 TDT 5-01/SGO7 27 -MAR -88 FLOWMETER 5-01/SGO7 27 -MAR -88 TEMPERATURE SURVEY 5-02/SG10 20 -JAN -88 TDT 5-02/SG10 30 -MAR -88 FLOWMETER 5-02/SG10 23 -APR -88 TDT