X-Field Study Report

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Port Said University

NGEP

X-Field Reservoir Simulation Study History

Matching & Prediction

Q1 2011

Prepared By:

1-

2-

3-

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5-

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X-Field reservoir simulation study

RESERVOIR SIMULATION

Contents

1PREFACE ..........................................................................................................................3

1.1Reporting Structure.......................................................................................................3

1.2Audit Process................................................................................................................3

2EXECUTIVE SUMMARY....................................................................................................4

3INTRODUCTION................................................................................................................5

3.1General Comments.......................................................................................................5

3.2Software.......................................................................................................................5

4X-FIELD HISTORY.............................................................................................................6

4.1Production....................................................................................................................6

4.2Pressure.......................................................................................................................7

4.3Previous Simulation Modelling......................................................................................8

5PHASE 3-1 RESERVOIR ENGINEERINGNUMERICAL SIMULATION AND HISTORY

MACTHINGRESERVOIR ENGINEERING ANALYSIS.........................................................9

5.1Completion and Workover history.................................................................................9

5.2PVT Data Characterization...........................................................................................9

5.3Routine Core Analysis..................................................................................................9

5.4Saturation Functions...................................................................................................10

5.5Capillary pressure data...............................................................................................10

5.6Historical Pressure, Production data...........................................................................10

6MODEL CONSTRUCTION...............................................................................................11

6.1Base Geomodel..........................................................................................................11

6.2Fluid PVT Properties...................................................................................................13

6.3Relative Permeability & Capillary pressure data.........................................................14

7MODEL INITIALIZATION.................................................................................................15

7.1Initial Saturation & Pressure.......................................................................................15

7.2Initial Fluids in Place...................................................................................................16

7.3Well Definitions...........................................................................................................17

7.4Primary Uncertainties..................................................................................................17

8THE MATCHING PROCESS............................................................................................18

8.1Objectives...................................................................................................................18

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8.2Match Criteria.............................................................................................................18

8.3Global and local Modifications....................................................................................18

9HISTORY MATCH DISCUSSION.....................................................................................27

9.1Purpose of Simulation.................................................................................................27

9.2History Matching Process...........................................................................................27

9.3Match Criteria.............................................................................................................27

9.4Match Reliability..........................................................................................................27

10PRODUCTION PERFORMANCE FORECAST...............................................................28

10.1Base Prediction (Do nothing) Strategy......................................................................28

10.1.1Case 1..................................................................................................................................................28

10.2Work-over Strategy...................................................................................................28

10.2.1Case 2 ................................................................................................................................................ .2810.3Convert Producers into Injectors Strategy.................................................................29

10.3.1Case 3 (PROD_1 Converted to injector)..........................................................................................29

10.3.2Case 4 (PROD_2 Converted to injector).........................................................................................29

10.3.3Case 5 (PROD_3 Converted to injector).........................................................................................29

10.4Drilling new producers Strategy................................................................................29

10.4.1Case 6 (PROD_6).............................................................................................................................29

10.4.2Case 7 (PROD_7)..............................................................................................................................30

10.4.3Case 8 (PROD_8).............................................................................................................................30

10.4.4Case 9 (PROD_9).............................................................................................................................30

10.5Drilling new Water Injectors Strategy........................................................................30

10.5.1Case 10 (INJ_4)................................................................................................................ ........ .......3010.5.2Case 11 (INJ_5)................................................................................................................ ........ .......30

10.6Combination Strategy...............................................................................................31

10.6.1Case 12 (Combination) PROD_6 + PROD_7 + PROD_8 + WO.................................................31

10.7All Cases description & Summary results ................................................................31

10.8Cases Oil & Gas Reserves.......................................................................................32

11CONCLUSIONS & RECOMMENDATIONS....................................................................33

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1 PREFACE

1.1 Reporting Structure

This report documents represent Phase 2 of the Reservoir Simulation Study for the X-

field. The study is divided into 2 phases as follow:

Phase I: Supplemental of Geological& Geophysical & Petro-physical and Static

Modelling study for X-Field.

Phase II: Dynamic Reservoir Modelling study for X-Field.

Phase 1 was supplemented by the Exploration team using the geological and

geophysical information then we got the static model data.

The objective of Phase II of the project is to create a dynamic simulation model for the X-

field suitable for comparing different development plans. This work comprised the

production of a revised static geological model and the reduction and evaluation of

reservoir engineering data to develop this dynamic model. The elements of this work

were brought together in a geo-cellular model and output in a format suitable for input to

the reservoir simulator (Geoquests Eclipse).

1.2 Audit Process

The work will be subjected to auditing process by experts in Port Said University-NGEP.

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2 EXECUTIVE SUMMARY

An adequate history match of observed X-field performance has been achieved by

making reasonable changes to the magnitude of properties in the original geomodel and

the engineering data. The overall match for historical data is very good. The water and

gas rate match obtained is adequate.

Despite the fact that the pressure history match of the model is considered very good, the

available shut in historical pressure points available for use in pressure history match

were limited and dont cover the whole production period but the bottom hole flowing

pressure values were enough and cover the whole production period.. Regular, long-

term, build-up tests and static surveys should be performed on monthly basis, at a

minimum, for the key production wells.

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3 INTRODUCTION

3.1 General Comments

It is generally recognised that reservoir simulation is an approximate mathematical

representation of reality. Simulation however remains the only viable method of producing

credible production forecasts of multi-phase flow from complex geological structures.

The term History-matching describes the process of adjusting model inputs (geo-

parameters) within reasonable limits such that the outputs (pressures and flows)

predicted by the model reproduce historically observed data. This process of model

calibration is frequently very time-consuming and always non-unique (i.e. there is never a

perfect match); it does not necessarily follow that a well-matched model will yield reliable

predictions. It should be stressed that prediction cases performed following history-

matching are estimates of future production, rather than being regarded as the truth.

Throughout this document, suggestions and recommendations are made to assist in

improving the model and further increasing confidence in its predictive capability.

3.2 Software

Reservoir simulation which was reported herein was performed using Geoquests

Eclipse 100 numerical reservoir simulator. , Other analyses & interpretations were

performed using Microsoft Office.

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4 X-FIELD HISTORY

The X-Field has been under production since Q1, 2000 and since start of production we

the water injection started. Initial volumes in place are estimated to be approximately

517.22 MMSTB Oil in-place and 629.09 BCF Gas in-place. The original GOC & OWC

was located at -5512 & -5590 ft TVDss respectively. The initial reservoir pressure at the

datum depth of -5512 ft TVDss is around 3500 psia, which is very close to the bubble

Point pressure which was measured to be +/-3320 psia.

The primary production mechanisms in the X-Field are oil expansion, aquifer support,

through aquifer, Gas support from the gas cap, and Rock compression has lower order

effects.

4.1 ProductionThe X-field commenced production in Q1 2000 from five wells

PROD_1,PROD_2,PROD_3,PROD_4, and PROD_5, producing at circa 24000

STBO/DAY with 0 % water cut. Production increased substantially to reach 30000

STBO/DAY in Q3 2000 with 0% water cut the production reach its peak of 35000

STBO/DAY at the beginning of Q1 2003 with water production rate 4000STBW/DAY.

Then, Production decreased gradually to reach 14000 STBO/DAY in Q4 2010 with water

production rate 26000 STBW/DAYT the historical oil , water , and gas production rates

and its comulatives for X-Field are shown in the bellow figures.

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4. 2

Pressure

The pressure behaviour observed historically supports the statement that driving

mechanisms in this field are oil expansion and partial aquifer support and because of this

weak aquifer support water injection rate started from first day of production, the figure

bellow she the historical shut in and flowing pressure data for all X-Field wells.

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4.3 Previous Simulation Modelling

No previous simulation studies implemented for this field and this study considered being

the first study.

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5 PHASE 3-1 RESERVOIR ENGINEERINGNUMERICAL SIMULATION ANDHISTORY MACTHINGRESERVOIR ENGINEERING ANALYSIS

Basic reservoir engineering techniques are used to build enough reservoir knowledge

prior to the simulation model construction.

5.1 Completion and Workover history.

Completion, testing and workover histories for all wells have been collected and data

based to ensure that significant events are incorporated in the SCHEDULE of the

simulation model and that vertical resolution in the model is sufficient to model these

events adequately as it affect in the well productability which is function of wellbore and

reservoir properties.

WellName

X,ft Y,ft Top,ft Base,ft Upper_Perf,ft Lower_Perf,ft Skin

Prod_1 6500 -7500 5400 5900 5500 5700 5

Prod_2 8500-15500 5600 6100 5650 5800 1

Prod_3 7500-13500 5540 6040 5590 5790 3

Prod_4 3500-14500 5400 5900 5500 5700 0

Prod_5 3500 -8500 5400 5900 5500 5750 2

Inj_1 8500 -1500 5850 6350 6050 6350 0

Inj_2 2500 -1500 5700 6200 5900 6200 0

Inj_3 5500-19500 5540 6040 5740 6040 0

5.2 PVT Data Characterization.

The PVT data/fluid analysis reports have been reviewed and evaluated to establish acoherent set of PVT properties for use in the remainder of the work. QC of collected data,

procedures, and measurements has been reviewed accurately. In our case, we have 2

PVT samples one for the gas and another one for the oil, and after analysis we used one

PVT table in the simulation work.

5.3 Routine Core Analysis.

All the reservoir rock properties have been reviewed and analysed to obtain the available

data such as Horizontal Permeability, Vertical Permeability, Porosity, initial water

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saturations, and rock types by applying the suitable techniques. The conventional core

analysis results are used as a guide for the static and the simulation model.

5.4 Saturation Functions.

There were no SCAL analysis data for this field then Corey correlation was used to

estimate the relative permeability curves for oil, water, and gas.

5.5 Capillary pressure data.

There were no SCAL analysis data for this field then correlation was used to estimate the

relative permeability curves for oil, water, and gas.

5.6 Historical Pressure, Production data.

The historic data have been reviewed using plots and maps. Data analysis provided abig picture of the reservoir behaviour and probable un-swept areas. QC of the well test

data has been performed. All pressure data are corrected at the datum selected for the

simulation. Production histories have been reviewed and allocation volumes compared

with available test data, and the production allocations have been revised. Attention have

been paid in particular to water-arrival time and development of water-cut behaviour

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6 MODEL CONSTRUCTION

During this study, a model with a number of different realizations was constructed and

tested.

6.1 Base Geomodel

The derivation of the X-Field geomodel is discussed in detail in the static model report.

The simulation grid was output in Eclipse format, the Schlumber Geomodelling software,

with the following dimensions:

NX = 12, NY = 22, NZ = 10

The model Top Structure array is shown in plan view in the bellow figure. The average

dimensions of DX and DY are 1000ft and 1000ft respectively. The Dz in the X-Field is

50ft to allow better representing for the smallest perforation thickness, and also to allow

better vertical properties distribution.

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The horizontal and horizontal permeablilities and porosity distribution in the X-Field model

are shown bellow.

The total number of cells in the model is 2640 cells of which 2240 are active, the cells

which do not show any pay represented to benon active. This keeps the model run time

practical.

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6.2 Fluid PVT Properties

Oil, Gas and Water PVT Properties were derived from PVT analysis of down-hole

samples. Oil PVT Properties used in this study is shown in the bellowFigure.

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6.3 Relative Permeability & Capillary pressure data

There were no SCAL analysis data for this field then Corey correlation was used to

estimate the relative permeability curves for oil, water, and gas, and other correlations

used to estimate the capillary pressure data.

The Oil, Water, and Gas relative permeability and capillary pressure data are shown

bellow:

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7.2 Initial Fluids in Place

Initial volumes in place are estimated to be approximately 517.22 MMSTB Oil in-place

and 629.09 BCF Gas in-place.

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7.3 Well Definitions

The schedule was created with 5 vertical producers and 3 water injectors.

Wells were put in groups, according to their location.

7.4 Primary UncertaintiesThe primary uncertainties for the built model fall into the following categories:

1. Aquifer strength and connectivity parameters.

2. Relative permeability data.

3. Absolute permeability.

4. Vertical permeability.

5. Porosity.

6. Fault transmissibility data.

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8 THE MATCHING PROCESS

8.1 Objectives

The term History-matching describes the process of adjusting the model inputs

(geo-parameters) within reasonable limits such that the outputs (pressures and flows)

predicted by the model reproduce historically observed data. This process of model

calibration is frequently very time-consuming and always non-unique (i.e. there is

never a perfect match); it does not necessarily true that a well-matched model will

yield reliable predictions.

8.2 Match Criteria

The general criteria for the history-match are as follows: field cumulative oil

production and oil production rate must be matched. Water rate should be matched

within +/- 10%, provided that W.C trends match the observed ones. Pressure data in

the majority of the wells should be matched to within +/- 200 psi. The most recently

acquired observed data are given highest weight in definition of the match.

8.3 Global and local Modifications

During this study, a number of global parameters were selected for modification by

ECLIPSE to obtain the global optimum history match. The selected parameters

include Corey parameters for relative permeability data, porosity multipliers,

permeability multipliers, aquifer volume, and aquifer productivity index. An overall

adequate history match was achieved using this approach after several sensitivities.

It was clear after these runs that some wells have poor match for flow rates and

pressure. So a decision was made to carry out some local modification around poorly

matched wells. The final modifiers values can be found in the data file.

The history match results are illustrated in the following figures:

The following figures show the rates match. First achieved the liquid rate match on

the field rates, and field total production. Then, by back allocation achieved rates

match on the wells (oil & water rate).

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9 HISTORY MATCH DISCUSSION

9.1 Purpose of Simulation

Reservoir simulation is frequently the only viable way of forecasting production from

hydrocarbon accumulations. The history-match process, whereby the underlying

geomodel is calibrated to reproduce observed behaviour, helps to overcome many

of the uncertainties associated with the approximate nature of the initial geological

description.

9.2 History Matching Process

Add aquifer for pressure support.

Change layer permeability

Adjust transmissibility to control water movement (Tran X, Tran Y, Trans Z)

Where necessary modify porosity

Mechanical skin.

Change transmissibility values of the fault.

9.3 Match Criteria

During the history matching process the following criteria are used in order to achieve

SD3 field history matching:

Field cumulative oil production and oil rate.

Field cumulative water production and water rate.

Field cumulative gas production and gas rate.

Water cut match to be within +/- 10 %.

Pressure match to be within +/- 200 psi.

9.4 Match Reliability

The overall match quality for the field and single wells is considered Very. Good for

this model. It is adequate for the purposes of comparative performance predictions.

It is recommended that further pressure data be acquired to allow the model to be

updated and revised.

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10 PRODUCTION PERFORMANCE FORECAST

Based on the history match described in the sections before a base case and other

prediction cases were performed in order to predict the production performance of

the X-Field under different development scenarios. High level overview of the results

for the development scenarios are listed in the next section of this report.

The following assumptions are applied:

Minimum bottom hole flowing pressure is 200 psi.

Maximum water cut is 100%.

Production rates at the start of prediction are similar to the end of history

match.

Injection rates at start of prediction are similar to the end of history match.

Minimum spacing between the wells is 1000 m.

Runs are done Dec 2020.

10.1 Base Prediction (Do nothing) Strategy

This is a run with the existing wells constraints without adding new wells orincreasing the current off take. Individual well liquid producing rates are adjusted to

values at the end of history matching.

10.1.1 Case 1

The forecasted Oil Reserve is 131.04 MMSTB cumulative productions with, 25.34%

oil recovery factor & the forecasted Gas Reserve is 227.09 BCF cumulative

productions with, 36.10% oil recovery factor.

10.2 Work-over Strategy

In This case we multiplied the PI for all the wells by 2 as a result of a successful

stimulation job, then we increased the well production and injection rates by 1.5 times

end of history machining values.

10.2.1 Case 2




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10.3 Convert Producers into Injectors Strategy

In this development strategy we converted the high water cut wells from oil producers

into water injectors on 1 jan 2011 with injection rate 20000STBD.

10.3.1 Case 3 (PROD_1 Converted to injector)









The forecasted Oil Reserve is 124.4 MMSTB cumulative productions with, 23.98% oil

recovery factor & the forecasted Gas Reserve is 218.08 BCF cumulative productions

with, 34.67% oil recovery factor.

10.4 Drilling new producers Strategy

In this development strategy we drilled new oil producers in the upswept oil regions ,

the liquid control rate for the new well was 7500 STBD.

10.4.1 Case 6 (PROD_6)




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10.4.2 Case 7 (PROD_7)




10.4.3 Case 8 (PROD_8)




10.4.4 Case 9 (PROD_9)




10.5 Drilling new Water Injectors Strategy

In this development strategy we drilled new Water injectors , the water control rate forthe new well was 20000 STBD.

10.5.1 Case 10 (INJ_4)


oil recovery factor & the forecasted Gas Reserve is 218.74BCF cumulative


10.5.2 Case 11 (INJ_5)




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10.6 Combination Strategy

In this development strategy we select the best from all the previous cases in one

case.

10.6.1 Case 12 (Combination) PROD_6 + PROD_7 + PROD_8 + WO




10.7 All Cases description & Summary results

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S t r a t e g yD i s c r i p t i o nC a s e _ N a m eC o n vw e l l s p

S t r a t e g y 2W O P R E D _ C A S E 2

P R E D _ C A S E 3P R O D _

P R E D C A S E 4P R O D

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10.8 Cases Oil & Gas Reserves

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11 CONCLUSIONS & RECOMMENDATIONS

Models are a useful 3-dimensional dynamic tool for reservoir management to

aid the evaluation of various enhancement projects such as Water flood value

water shut off workovers, pump upgrades, re completion and wellbore

utilization decision

The field has an estimated 517.22 MMBO STOIIP Oil in place

The field has an estimated 629.02 BCF Gas in place

Excellent History match has been achieved

Recovered 17.7% of original oilinplace to date

Reservoir has a weak water drive mechanism

The run with the existing well constraints without adding new wells or

increasing the current off take will recover around 131.04 MMSTB cumulative

oil productions, 25.34 % recovery factor.

Drilling new 3 producers + work over for all the wells will produce oil reserve

140.9 MMSTB with RF 27.24% & Gas reserve 441.94BCF with RF 70.26%.

X-Field Study Report

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