SPE ScmrrW of M. Mr!rnn
SPE 23142 A New Method To Monitor Compaction and Compressibility Changes in Offshore Chalk Reservoirs by Measuring Formation pressure variations Caused by the Sea Tide
and R, Hardy, Amerada Hess Ltd., and P. Eltvik, ” Amerada Hess Norge A/S
Copyright 1991, Society of Petroleum Englneere, This paper was prepared forpreeentalion
Inc. held in Aberdeen, 3-6 September 1991.
al Ihe Ollehore Europa Conference
Thie papar wae selected for preeentalion by an SPE Program Commmee following reviaw of information contained in an abslrect eubmitled by tha author(e), Contonls of the paper, aa presenled, have nOlbeen reviawed by lhe Society of Petroleum Engirmers @nd are eubject to correction by lho author(s). Thematerial, ae pre$onlocl, does not rmceasarily reflcrcl any position of the Society of Petrolaum Engineere, its officers, or members. Papera preeented at SFIE meelinga are aublec! to publication review by Editorial Cornmitteea of the Society of Patroleum Engineers. Permission 10 coPy ia restricted 10 an afMact of not more than 3tM words. Illustrations may not bo copied. Tho abstract should containconspicuous acknowledgment of where and by whom the peper is presented. Write Librarian, SPE, P.O. Sox 833836, Richardson, TX 75083.3036 U.S.A. Telex, 730989 SPEDAL.
lNTROLNJfTflON Some 01 Ihc NorIh ,!’a’s hrrgesi utsd nmsI imporlo.nt oilticlds wc in ckrfk rcscrvrsirx. III I!rcsc field.s i[ is imprrmrnt 10 Incmsr-s the compaction and compressibility bccarssc the comfmkxr cam rcsrdl of IIWrc.wrvoir in plwf’rxm subsith!occ,“ 1 srwh lcsls il is ofiwl nw’ssiiry pressure variirriotas 10 Iirxl remrwc Itsc Iormirtion
rnwfc by fhc (idal elfcc( heforc prcmxfing llrc grul mojonty 01 the Iwls with USC (cst mlcqwvkrlion. is Ixcacrw lhc prcswm variations cwrscd hy tlw !irle are small
however arc nol af’lccrcd significantly by drc tidal et’lcct. Ilis in compwison 10 Ihc pressure chaogcsnwascrnxf in ir WSI. Typically the tidal lom~ation prcssum variations for North Sca smnbslorw nwxvnirs WC in Ihc rmgc 0.1 - 0.5 psi [,7 - 3.5 kpa], On ~ pi~r Iicld, for cxislllpk!, Iflr! Iidl] WSCIVOb prcsscrrv varhitirsrr was 0.2 psi @klo-fwrft [ 1.4kPa]$’
Alsrt a nurjor drive mcctmnism in Ihcsc IielrLs is conlpirciinn drive sod so an accumtc cslimirtion of ruscrw cmnot lx muck witboul firwrncssurirrg ccm possibility. Estimirting compmion and rcsc vcs k diflhsh Usc field Iifc,] The imtidltilioo rncthod ~ of wcumlc pcmmcm downholc prwsurc twxsuac comprwsibili!y ctumgcs dcning
gaugc!son offsk ‘,rv cbidk ficlch makes it possible to usc a ncw tire Illurscrn!nlcnt of 10 rnon.hor compresaibilily: The (irfal
All reservoirs UK irffcclcd m some cxtr!m by the tidal cffccl. TfK! moon and suncxcrl a tiduf pull noI just on the sca bcn sfso The air Iirfc ciur bc nmrsrmi mfcrrud [o w as IIVJ on the air and Ihc carlh.
ruscrvrrir prm..urc changes ciruscd by the tirlc. inctwc infom]aliuo obrxstcompressibility. arrd 10 nmsuw with drnc, on Ihc appliculion of
nmrritrrring tcchniqrrc is an in-silu mcltnsf which cin gnwlly II can lx uscrf both WC variation in to csfinMIc cornprussibiliiycrsmprcssibility
bisromc!tric chirnges and so is r)llcn
“biiron)ClriC” tide, The culh tide results in only a tiny dc fonnti(ion 01 Ihr! c!artb’s scrrfiicc: k! maximum dclommlion of IlSQcanh’s srsrfirccis only 36 cm 114 in],ti Nrwcrtisic$s IIVJ isttcmpt by tlrc solid Lwnh’s crus~’to deform under griivilationirl
rnorriloring tcclmiquc 10chalk rwscrvmrs in IIKI NoIlh
clungcs ICSUIIS in nmscrrablc chan~cs in rvscrvoir Iorrnalion prvssurw. Tkc am marIy prrblislwf cxiunpk!s of obscwrliom mask in WCIIS of fhc sir tide” “’9 and ttrc ctih tidc9’ ‘“”‘“ ‘~’‘“ Ii ~,, M()$t “f ~K,%, ‘)b,~rvati~]s have bwn mirdc ill WatCr WCIIS or gcuhwrnaf As obscrvistiuos. wclle mostly in Ilrc conikreniid United Slams. is uwsafly abscul front tfrcac...