ASSIGNMENT-II

ASSIGNMENT-IIPetroleum Formation Evaluation

Submitted to :

Dr V. P. SHARMABY:

YOGESH MOHAN

ADM. NO.-9971

6TH SEMESTER

B-TECH (PETROLEUM ENGG

1. SOLUTION:Formation Evaluation of wildcat well A number of details and specialty of well and field decide the suitability and worth of running a particular log to a wildcat well .It is impractical to think of a universal log applicable to all well or field conditions. So the following points must be well-discussed while deciding the most effective combination of tools to be used:1. Lithological geometry of zone including type, thickness, variation of productive zone.2. Physical nature of zone (sand consolidation, litho logy, fracture) & hydrocarbon (crude type, T,P) and chemistry of zone element content.

3. Previously available data history of area.4. Drilling technique (knowledge of zones in vicinity of objective formation) & drilling fluid usedZONE CONDITIONLOGGING / TOOL PACKAGE

Formation water in productive zone- from fresh to mildly saltyUn/partially-consolidated & poorly sorted sand, clay presenceHeavy drilling mud,Lots of heterogeneity Mud logging for all wildcate well, coring(diamond) & testing (depending on show)

Induction-log replaces resistivity log

Micro log(non-focused is even fine) /sonic log is run in nearly all wildcat well

While radioactive log (rarely due to poor contrast) until precise depth locating is a need.

SP log to get Sw if salty formation water

Productive Formation water : very saltyUnconsolidated but well sorted sand ,Shale sloughing possibilityFracture-less & carbonate-free zoneDrilling mud : heavyMud logging for all wildcat well

coring & wire line testing (depending on sidewall sampling/show & result of mud logging)

induction-log & micro log (focused for thin sand)/sonic log for nearly all wildcat well

No open-hole test to avoid sloughing

Formation water :fresh to moderately saltyFormation rock :hard Irregular & fracture porosity in sandstone, carbonate & shaleChemical nature (huge anhydride content)Fair homogeneityMud logging & coring /testing (open hole)(diamond as formation is hard)for all wildcat well

Sidewall sampling is ineffective (due to hard formation)

SP log is dampened due high resistivity

Micro lateral log (focused for thin sand)

Gamma & neutron in all exploratory well(due to high radioactivity content)

Sonic /porosity log for porosity

Formation water : highly saltyIrregular & fracture porosity in sandstone, carbonate(vugs)Salt mud for salt thick bedsMud logging for all wildcat well

Cutting oil show to reveal production from carbonate reef.

Coring to get ,k

-log in place of SP

Micro log for qualitative

Mostly open hole testing

Formation water : very salty Irregular & fracture porosityCarbonate formation Salt mud for thick salt beds

Mud logging for all wildcat well to guide coring ,logging & testing

Special method (using current focusing )to calculate saturation

Sonic /gamma log for

Log Quality Control CheckActually, Qualitative & quantitative accuracy & reliability of logging are matter of well-functioning of tools and sincerity of loggers. So to avert the situation of equipment failures & operational difficulties, which lead to quality-degradation of log, geologist and engineers are supposed to do threadbare pre-log, on-log & post-log analysis . Only worth-running log should be performed only to avoid financial & operational botheration. Re-running of log should be considered to correct any suspicion arised.

Pre-log Preparation:(A) PROPER COMMUNICATION WITH SERVICE PROVIDER

1. Make the service company know the kind of log you need to be run & an any extra technical details which may help in selection of main & accessory equipments or in taking precaution .Ex: in case of Unusual high pressure & temp of well etc.

2. Always, effort should be made to employ best person on the job ,because interpretation of data is even more important than just operation.

(B) WELL PREPARATION

1. All data related to well(name , location ,correct elevation ) or field (field name ) like inferences made on mud samples and details like hole size, total depth , casing size , mud weight & viscosity, borehole temperature & condition , should be checked and disclosed to engineer in the process.2. Equipments & engineer on duty should be ready with all necessary decision as soon as tripping ends. GENERAL CHECK FOR ALL LOGS ON-LOGGING 1. Dont destroy print detail of anything that happens during logging including even calibration to outcome of any unsatisfactory log.

2. Scale which could give best contrast of parameters involved should be chosen. SPECIFY at top & bottom in printed form for every scale change made.

3. Do try to get very precise and volumes of data to facilitate further interpretation & unnecessary assumptions to be made in want of sufficient data.

4. Always attention should be paid for proper hardware co-ordination & proper functioning of any newly introduced tool.

5. Depth control- takes a scale like 1ft -1000 ft depth with error approximation +1 ft at any depth. Cable must be tight while running the tool otherwise reading will mismatch.6. Anything special regarding formation under-consideration should be put down as remarks.

7. Header and footer of printed should include clear-cut information of well (specification),a note of service performed by company.SPECIAL QUALITY CHECKLOGGING SPECIAL CHECK (OTHER THAN GENERAL)

SPGround electrode is to be kept stable in the stagnant mud of pit

Extraneous noise from any source (generator, radio etc) need to be zeroed.

Logging speed should not be greater than 6000 ft/hr(for good sensitivity of galvanometer)

In post analysis check of any superimposition of constant frequency & also other roots of erroneous SP curve.

INDUCTION LOGProper scale selection for good plot

TO record calibration & zero check on wooden horses in hile at bottom & at top

Have mechanical zero reading at bottom & top & electrical zero for pipe

15 minute warm up for tool must be given

Again tool speed6000 ft /hr.

MICROLOGA good sample of mud of known Rmf & Rmc is neededMicro log should always be run with caliper log.Obtain mechanical zero reading at bottom & top & electrical zero for pipe.

Use expended depth scale for very thin interbeded zone.

SONIC LOGCarbonate section should be logged with more sensitive scale

Obtain mechanical zero reading at bottom & top & electrical zero for pipe

Again, tool speed6000 ft /hr.

Have sonic log recorded across two track

Centralizer must be used with tool if seismic velocity information is needed.Check for cycle skipping /triggering

CALLIPER LOGPrecision of SCALE is quite important (1/8).

RADIOACTIVE LOGSpecify the type of tool used-detector & its length ,neutron source, source detector spacingDo a 2-3 minute stastical check in dense zone for the neutron & shale for gamma log

Use short detector for thin bed

SOLUTION POROSITY of formation = = Where F=Ro/Rw