MEETINGS HQS DINNER MEETINQ AND POSTER SESSION-APRIL 13, I D 9 2 Social Pwlod, 6:SO p.m., Dinnr and Meeting, 6:30 p.m. Poot Oak Doubletno Inn displacements are postive throughout. MCS automatically

processesa normal fault. When dieplacementsare negative. RICHARD 8. BANKS-Biographical Sketch MCS processes a reverse fault. Sciiwrs faults result fron

displacements which change signs within the mapped area. r B' Banks Areas with zerodisplacement show wherea fault ceased tc ceivedanEnwrofGe exist. Some growth faults can be modeled with displace- physics dwee lrom ments which show weat variation across the mappedarea rado School of Mines in The user of MCS should (usually) first analyze the fault Master's system by making contour maps or cr-sections of all the in Petroleum Enginoerbrg faults in orb to: from the University of Texas at Austin in 1957. 1. Test the faultsfor reasonableness, e.g.. do observed

After twelve years with fault cuts that have been assigned to the same fault

Pan American Petroleum result in a picture that makes sense?

Corporation as a petro- 2. Infer and/or ascertain the hierarchy of the faults.

leum engineer, Mr. Banks i.e., when two faults meet in space. which one

became President of Scien- survives? Which one is, therefore, older?

tilic Computer Appli- 3. Infer andlor ascertain which faults form boundaries

cations, Inc., Tulsa, of a fault block. The analysis easily lends itself to "what if" games, i.e.. Oklahoma' Since he the testing of various hypotheses. has been responsible for The instructmns MCS needs to perform its task are a economic evaluations and development of an integrated set Of RESTOREcommands, each a fault graphics and economics system which is widely used block and irrseucts MCS to it to its pre.faulted throughout the petroleum industry. position. The RESTORE commands takes us "back in His professional affiliations include: Wstered Pro. time;' is. the tvst m~~~~ revem the most recent fessional Enginear in the State of Okbhoma. faultingevent, the bst RESTORE reverses the oldest event Professional Engineer in the State of Texas, American

Asswiation of Petrohum Geologists, Society of Exploration The sequence and makeup of the RESTORE instruc- GeophVsicists, of Engineers, of tions is derived horn an analysis of the fault and any a priori

PetrolPum Evaluation Engineers. knowledge of the area. Consider a sytem with two antithetic bulb Fault 'A'

RIGOROUS COMPUTER PROCESSING OF and Fault 'B', both of which are shown in Figure 1. S i e MULTIPLE NON-VERTICAL lMERSECTING Fault 'B' dies against Fault 'A', Fault '6' is presumed to be

FAULTS AMONG MULTIPLE SURFACES younger. Fault 'A'is presumed to be the olderfault,and the system can be divided into three blocks: 1) Abwe 'B' and

pMaping-Contouring System (MCS) treats faulted above 'A', 2) Below '8' and above 'A', and 9) Below 'A'. systems* what they am Sets of threedimensional blocks In keepingwith the principlethat RESTOREcommands containing geological mdrkers (formation tops) which once are taking usaback in time:'wemust restore first the block were continuous surfaces. The boundaries 01 these hull which waa displaced during fault event 'B'. 1.e.. the Mock Mocks are contourable surfaceeand are the tault surfaces. which lies abow 'B' and abow 'A', hence:

MCS processes fwltedsystemsin threestepsdesigned to honor continuity of shape across faults RESTORE (Above) 'B' A h 'A'

1. MCSRrstmoves the fault blocks to their pre-faulted Next we must restore the block moved during fault positions together with the contained formation event 'A' which is the block above Fault 'A' and which. tops. Incidentally, contains Fault 'B':

2. Then. having restored the "Continuws surface" athibute to the geologicmarkers, MCS performs all RESTORE (Above) 'A' the "Stacking" (diiussed later) and interpolations When MCS has finished complying with these com- needed to obtain a smooth map or crosksection. ma& it would have, in effect, accomplished a vertical,

3. The thiidstep is to rebreak, 1.e. reverse the firststep sequential, three-dimensional palinspastic reconstructionof and return the fault block and their contents to the fault system. Now that the faulted system has been their faulted positions, and to display as contour restored to its pre-faulting configuration, the structural maps or cmswections. surfaces are continuous and can be stacked.

To accomplish these steps MCS needs certain data and a set of instructions: M ~ S u r f s c a Stacking:

ToMCS, faultverficaldisplacement or vertical separa- In areas of coaformable geology. adjacent formations tlon Is just another mathematical surface which can vary resemble each other. MCS uses the principle of con- over the mapped area and can be contoured. When formable geology in itsmulti-surfacestacking process. MCS

s Y l r r n ~ o ~ J r * , , . 4 m I 9 1 2 12

first calcit la~cs isopachs (differences in value herween xliacent w r t x e s ) wherever possible. These lsopachs are ~nrrrpolated o r cx~rapoiatedover theentiremaparea for all !soparii tn:crvals. Calculated isopach values are added or suhtr;lcted i t om known daiums in order l o reconstrucl a cnmpletr set of l values at all d a ~ a points. This "starking" procrcds d~wn rva rd firs1 and upward srrond.

As A rchult of fa& r s t o r t i i i and multi.surface starking there is a cont inu i~y of shapes (geologic fealures) across 1a~ii1<. atid MCS does reasonable con lour in^ in lault

4

Idorks d+n have no well or seismic control.

F ina l S tep in Faul t Processing Thr 11n.d step in MCS fault processing is to re.break

and tmve geologic surfaces to their true (post-faulted) pos~lions. This step is the mathematical inverse o l rest~r - rattnn. MCS generates lault traces as the intersection h r ~ w e e n structural surfaces and faults. Rigorous displace- met11 o r separation halance IS achieved at all laiilt inler- sections. F:gurrs 2 arid 3 show conlour maps lor the 8500- FI. and 9201'1.Ft. sands.

Figure 2

Figure

*

TOP 8600-FT SAND

TOP 9200-FT SAND