Horizontal Well Testing

 

Horizontal Well Testing Testing

   

Well Test Interpretation Process • Well testing tries to describe an unknown system by matching parameters in a model to measurement 

Direct Problem Inverse Problem

   

Well Test Interpretation Model The complete interpretation model is made of the combination of the individual components

 Although number of interpretation model are limited ( five near -wellbore effects  , and  th effects two basic the reservoir  behaviors, thre ree e ty type pes scomponents of  outer -boundary   ), their combination can yiel yi eld d seve severa rall thou thousa sand nd diff differ eren entt in inte terp rpre reta tati tion on mode models ls to matc match h al alll obse observ rved ed well well beha behavi vior ors s

   

1. Horizontal well testing  With

the significant incr incre eas ase e in hor oriz izo ont ntal al dri rill llin ing g ac acttiv ivit ity  y   during recent years, pressure

transient behavior in horizontal wells has received considerable attention.  In

this section, the  specific  flow  regimes  developed  during  a horizontal  well  test   and  t  the he

interpretation  methodology used are briefly described

 

Horizontal ontal well testing testing - Test Configura Configuration tion Horiz

 

Horizontal ontal well testing testing - Well and Reservoir Reservoir Geometry Geometry Horiz

      

Horizontal ontal well well testing testing - Flow Regimes Regimes Horiz •   Pressure transient behavior in a horizontal well test is consider considerably ably more complex than in a conventional vertical well test because of  its three-dimensional  nature

 A ny flow reg ime may may be abs absent ent fr from om a plot of test data becaus e of g eome eometry, try, wellbore storage or other data becaus  factorss .  factor

     

Horizontal ontal well testing testing - Steps to Evaluati Evaluating ng Data Horiz St Step ep 1: Iden Identi tify fy Fl Flow ow Regi Regime mes s

Five major and distinct regimes possible – may or may not even occur – may or may not be obscured by wellbore storage effects, end effects, or transition effects St Step ep 2: Appl Apply y Pr Proc oced edur ures es

Estimate important reservoir properties – Determine parameter groups from equations – Expect complex iterative processes requiring use of a

computer St Step ep 3: Ev Eval alua uate te Resu Result lts s

Estimate important reservoir properties – Simulate test to confirm that the analysis is consistent

with test data –   Use Use sim simula ulator tor to det determi ermine ne whe whethe therr oth other er set sets s of 

formation properties will also lead to a fit of the data    

Horiz Horizontal ontal well well testing testing - Flow Regimes Regimes 1. Ea E arly R adia diall Flow Flow R egi me Initially flow occurs radially in a vertical plane toward the well  However due to permeability anisotropy the flow around the wellbore is not circular, circular, but elliptical, elliptical , as the pressure pressure  front will typically propagate more slowly in the vertical direction:

   

Horiz Horizontal ontal well well testing testing - Flow Regimes Regimes 1. Ea E arly R adia diall Flow Flow R egi me Initially flow occurs radially in a vertical plane toward the well mechanical  skin factor and the geometric average of the vertical and The first radial flow regime yields the mechanical skin a nd horizontal permeabilities and the ‘thickness’ ‘th ickness’ corresponds to the producing well wel l length

   

Horizontal ontal well well testing testing - Flow Regimes Regimes Horiz  2. Hemiradial Flow 

   

Horizontal ontal well well testing testing - Flow Regimes Regimes Horiz  3. E arly Linear   begins when the transient reaches reaches the toward upper and athe nd lower boundaries boundaries of the producing prod ucing interval and and flow becomes becomes linear well within a horizontal plane

estimate the length of the producing interval 

   

Horizontal ontal well well testing testing - Flow Regimes Regimes Horiz 4. Pseudoradial occurs as the transient moves deeper into the reservoir and the flow becomes radial again, but in the horizontal plane

yields the average permeability in the horizontal plane and the

total skin factor (mechanical and geometrical geometrical skin factors).         

Horizontal ontal well well testing testing - Flow Regimes Regimes Horiz  5. Late Linear “effects of pres s ur ure e reach boundaries in y   , z directions” 

Calculate total skin, st , including partial penetration skin, s p

   

Horizontal ontal well well testing testing - Flow Regimes Regimes Horiz

1. Phases in a horizontal horizontal well transient transient test. test. A fte fterr wellbore wellbore storage effects effects have dis dis ap appea peared, red, the flow flow is radia radiall toward toward the well in the vertic al y - z plane  2.

(fir s t plate plateau au in the deriv deriv at ative ive cur ve). The next phase is linear flow flow in the y  z - plane (s traig ht line with half - s lope in the derivative curve).

 3.

Fi nally nally flow  flow is radial in the x  y - y plane (second (s econd plateau in the deri vative curve cu rve

 

Horiz Horizontal ontal well testing testing - Deter Determine mine parameter parameters s Determine paramet parameter er g roups from equations equations

 

Horiz Horizontal ontal well testing testing - Deter Determine mine parameter parameters s Determine paramet parameter er g roups from equations equations

 

Horiz Horizontal ontal well testing testing - Summa Summary ry of Analysis Procedures Procedures

• Calculate k  x  data in early rad radial ial or hemir hemiradial adial flow regi regimes mes • Calculate k z from data • Calculate k y y from pseud pseudoradi oradial al flow regime regime • Check on expected durations of flow regimes using tentative results from the analysis to minimize ambiguity in results

   

Horizontal Horiz ontal well testing testing - Obsta Obstacles cles to Interpretati Interpretation on

• Multiple parameters frequently yield inconclusive test analysis results • Wellbore storage obscures effects of transient behavior  days, or late-time e response response behavio behaviorr may require several hours, days, • Middle- and late-tim months to appear in transient data

 

Horizontal Horiz ontal well testing testing - Obsta Obstacles cles to Interpretati Interpretation on

• Estimate horizontal and vertical k from tests in pilot hole before kicking off to hori ho rizo zont ntal al bo bore reho hole le se segm gmen entt stand ndof offf fro from m di dire recti ction onal al dr dril illi ling ng • Estimate sta survey

• Determine producing part of wellbore from fr om pr prod oduc ucti tion on lo log g flow flow surv survey ey lope ped d res eser ervo voir irs s lo long ng develo • Flow wells in deve enough to equilibrate pressures along the well we llbo bore re an and d mi mini nimi mize ze cros crossfl sflow ow

     

2. Analysis of Hydraulically Fractured Wells •   Hydraulic fracturing is a popular and effective  stimulation method. fracture is defined as a single crack initiated from the wellbore by hydraulic fracturing, that •   A fracture is by injecting a fluid (typically water with additives) at high pressure.

•   The fracture particulate material) with fracture is kept  open by  injecting  a  proppant (sand or similar particulate the fracturing fluid.

fracttured wel elll has has an in incr cre eased •   A frac productivity since the fracture provides an increased surface for the reservoir fluid to enter the wellbore.

 

 Analysis of Hydraulically Fractured Wells •   In addition to the usual reservoir characterization goals, well tests are performed in order to - investigate the efficiency of hydr hydraulic aulic fracturing jobs, jobs,  monitor any possible degradation of fracture properties due - and to to monitor properties due to production

         

 Analysis of Hydraulically Fractured Wells •   Rock mechanics suggests that the fracture fracture is always a   ‘bi-wing’  symmetrical geometry,  rectangles is  is an although our assumption in well testing that the fracture wings are 2 perfect rectangles over simplification

•  It is also assumed in the analysis of the fracture behavior that it is internally  propped to a constant  dimension, i.e. that there is no variation in fracture wi widt dth h wi with th heig height ht or le leng ngth th..

•  At present there is no way to know if this is true or not,

bu butt li likke all all math mathem emat atic ical al mo mode dels ls,, the the fr frac actu turre mode models ls are as good as can be handled analytically, and they typi ty piccally reprodu oduce the pressure response nse due to the  fracture quite accurately

dimensionless the wellbore radius is now an irrelevance, and in the dimensionless variables all ‘r w’ terms are replaced by another length term, ‘xf ’, the

fracture--half length fracture    

 Analysis of Hydraulically Fractured Wells  Flow regims

In the absence of storage, the first flow regime is a linear flow along the fracture axis ( red arrows), arrows ), which simultaneously induces a linear flow orthogonal to the fracture (blue ( blue arrows), arrows), the amplitude of which changes along the fracture length  This   bi-line bi-linear ar

flow flow regime regime, with with li line near ar fl flow ow alon along g 2 axes axes,, give gives s a pres pressu sure re resp respon onse se proportional to the fourth root of time.

 Both

the log-log and derivative plots exhibit  a quarter slope during bi-linear flow.

 Bi-linear

flow is followed by the usual linear flow, characterized by a 1/2-unit slope on log log

it just isn’ isn ’t significant compared to the linear pressure drop in the reservoir, into the fracture.

The bi-linear flow regime is a very early time feature, and is almost never seen.

finite-Conductivity Fracture

   

 Analysis of Hydraulically Fractured Wells  Flow regims

     

 Analysis of Hydraulically Fractured Wells  Flow regims

More surprisingly sur prisingly,, wellbore storage tends to be absent in the solution, as the productivity of fractured wells is so high that wellbore storage just isn’t seen in most cases.  The

fracture,, which is first flow regime seen in the pressure response is linear flow into the fracture

characterized by 1/2-unit slope lines in both the pressure and derivative curves

Infinite-Conductivity Fracture

     

 Analysis of Hydraulically Fractured Wells  Flow regims

When the distance the distance from the well to the pressure front is large compared large compared to the fracture length, we are in the fourth regime, (d), where the flow is infinite acting radial flow,  called  formation radial flow

The radial methods flow can be is using the for analyzed non-fractured wells wells. . standard In particular this means that permeability and skin is

found by fitting to a straight line on semi-log plot

   

 Analysis of Hydraulically Fractured Wells  Estimating parameters (bilinear flow)

If the fr frac actur ture e has a finite finite cond conduct uctiv ivity ity,, an early early flow flow perio period d with with   biline bilinear ar flow flow,, may be observed. This flow period can be  analyzed to obtain an estimate for fracture conductivity

   

 Analysis of Hydraulically Fractured Wells  Estimating parameters

There Ther e is an additio additional nal dimensionle dimensionless ss term in this model, model, FCD, FCD,   the dimensionless dimensionless fracture fracture conductivity, which takes account of the fracture width (w) and the fracture permeability (kf) and is compared to ‘kh’ :

     

 Analysis of Hydraulically Fractured Wells  Estimating parameters (linear flow)

a plot of pressure as a function of √ the period with formation linear flow will show a straight line with slope :

If  permeability is known, for instance from anal an alys ysis is of th the e fo form rmat atio ion n ra radi dial al fl flow ow pe peri riod od or from from a test performed pri rio or to fracturin ring, the slope can be use used to est estim imat ate e th the e fracture half length

     

 Analysis of Hydraulically Fractured Wells  Estimating parameters (pseudoradial  flow )

• Identify the pseudoradia pseudoradiall flow regime regime using the diagnostic plot • Graph pw pwff vs. vs. log(t log(t)) or pws pws vs log( log(Δte) • Find the slope m and the intercept p1hr of the best straight line • Calculate the formation permeability k from the slope and the total skin factor s from the intercept

   

 Analysis of Hydraulically Fractured Wells  Flow regims

   

3. Dual Porosity & Double Permeability Systems   Naturally

reservoirs   throughout fractured reservoirs  constitute a huge  portion   of  petroleum reservoirs 

the world, especially in Middle East.

  A

natur natural al fr frac actur ture e ar are e cr crea eated ted when when

stresses exceed the rupture strength of  the rock, rock, and the fracturing process is more prevalent in brittle rocks such as limestone,  as opposed to sandstone

 A naturally fractured formation is generally represented represented by a tight matrix rock broken up by highly permeable fractures

 

Dual Porosity & Double Permeability Systems

   

Dual Porosity & Double Permeability Systems  The

double-porosity (2Ø) models assume that the  reservoir  i  is s  not   homogeneous, homogeneous, but made

up of  rock matrix blocks  blocks,, with high storativit storativity and low permeability, permeability, connecting to the well by  fissures of  of low storativity and high permeability. natural fissures matrix blocks can not flow to the well directly, so even though most of the hydrocarbon the  hydrocarbon is stored in the matrix blocks it blocks it has to enter the fissure the  fissure system in order to be produced produced..

 The

 

Dual Porosity & Double Permeability Systems  The

dual-porosity model is described by 2 additional variables compared to the homogeneous

model:

1. w is the storativity ratio, and is essentially the fraction of oil o il or gas stored in the fissure system; e.g. w = 0.05 means 5%.

 

Dual Porosity & Double Permeability Systems  The

dual-porosity model is described by 2 additional variables compared to the homogeneous

model: 2. l is the interporosity flow coefficient and characterizes the ability of the matrix blocks to flow into the fissure system; it is dominated by the matrix/fissures  permeability contrast, k m/k f f .

   

Dual Porosity & Double Permeability Systems  Flow regims

1. When the well is first put on production, the the first  first flow regime will be fissure system radial flow i.e. the fissure system is producing, producing, and there is no change in pressure pressure inside the matrix blocks since sinc e th the e nec ece ess ssar ary y pre ress ssur ure e di difffe fere ren nce ha has s not ye yett been de deve velo lop ped 

  first flow regime is typically over very quickly quickly,, and is

 frequently masked by wellbore storage.   If not, it will be manifested by an IARF response on

the pre pressur ssuree deriv derivativ ativee

     

Dual Porosity & Double Permeability Systems  Flow regims

2. Once the fissure system has started to produce produce,, a pressure differential is established between the matrix blocks, still blocks, still at initial pressure pressure pi, and the fissure system, system, which at the wellbore has a pressure pwf .

The   matrix blocks then start to produce into the fissure system,, eff system effec ectiv tively ely pro provid viding ing pressu pressure re suppor support, t, and the  creating a transitional ‘dip’  in  in drawdown briefly slows down, down, creating the derivative. derivative.

   

Dual Porosity & Double Permeability Systems  Flow regims

3.   ‘Total system’  radial flow is established when any pressure differential between the matrix  radial blocks and the fissure system is no longer significant,  and the  ‘equivalent homogeneous’  radial flow response is observed observed - the second IARF line in the pressure derivative

(A (Ac ccordin rding g to th the e mat ath hemat atic ics s, this this tak takes pla lac ce when the the  pressure inside the matrix blocks is the same as in the fis fissur sure e sys system tem – but this could never be true at all points in the reservoir, as there would be no production into the fissure fissu re system.) system.)

the pressure front is spreading relatively slower than in the first period     

Dual Porosity & Double Permeability Systems  Flow regims

All of the pressure drop takes place at the surface of the blocks, as a   ‘discontinuity’,  and the

 transition:: resulting pressure response gives a sharp ‘dip’  during the transition

The derivative behavior for this case may look like the valley-shaped trend  As seen in this example, if the wellbore storage constant  (C) is very low, it may be possible to see the fissure syst system em ra radi dial al flow flow in earl early y time time.. Ho Howe weve verr with with a stor storag age e value of only 0.01 bbl/psi the first flow regime has alre alread ady y been been obsc obscur ured ed,, and and the the purp purple le curv curve e is typi typica call of  wh what at wo woul uld d be se seen en in a real real test test.. Th e

data

picks

up

the

dual-porosity

transition

immediately after storage effects are over, and this creat creates es a pot poten enti tial al uniq unique uene ness ss pr prob oble lem m with with the the data data set  set 

   

Dual Porosity & Double Permeability Systems  Flow regims

Although there are theoretically 2 IARF lines on the pressure derivative,   corresponding to 2 plot, the first is almost invariably obscured by wellbore parallel straight lines on the semi-log plot, storage

     

Dual Porosity & Double Permeability Systems  Flow regims

If seen, the 2 lines would each correspond to kf h, radial flow in the fissure system,



only ly the fi fiss ssur ure e sy syst stem em as in the first case on is pro produc ducing ing..



In the second case, although the total   system

is

producing,

any    pressure

differ diff eren enttia iall bet betwe wee en the ma mattri rix x blo lock cks s an and  d  the fissure system is now negligible , and  the only pressure drop in the system is in the fiss fissur ure es, as fl flu uid ids s fl flo ow to the well wellbo bore re

        

Dual Porosity & Double Permeability Systems  Estimating parameters

The dual-porosity dip in the derivative is defined by 2 parameters:

F or sm small all

values values

correspondingstored to a very high proportion of the , hydrocarbon in the matrix system, the ‘support’ during the transition is substantial, and the dip is deeper and longer 

The The st stor orat ativ ivit ity y ra rati tio o ex expr pres ess s ho how w much much of th the e to tota tall co comp mpre ress ssib ibil ilit ity y ca can n be at attr trib ibute uted d to th the e fractu fractures res,, and in a fractured reservoir    is small small::    < 10−2. In ot othe herr sy syst stem ems s with with du dual al por porosi osity ty like like pro proper pertie ties, s, suc such h as cer certai tain n hig high h con contras trastt lay layere ered d formati formations ons,,  ca can n be la large rger  r          

Dual Porosity & Double Permeability Systems  Estimating parameters

The dual-porosity dip in the derivative is defined by 2 parameters:

l controls the speed at which the matrix will react, and therefore determines the time of the transition: 

For a high l, the matrix permeability is comparatively high, so it will start to give up its oil (or gas) almost as soon as the fissure system starts to produce.



Conversely a low l means a very tight matrix, matrix, and more of a drawdown will have to bewill established in the fissure system appreciably give up their oil,  before the matrix blocks

The inter-porosity flow parameter express the strength of the fracture – matrix

coupling, that is the ability of the matrix to supply fluid to th e fracture system. Typical values for  is in the range 10−3 to 10−9.

and the transition is seen later       

Dual Porosity & Double Permeability Systems  Estimating parameters  In

terms of static variables the  dual porosity model is described using:

- one permeability (the bulk permeability of the fracture system   ), - two porosities porosities (the (the bulk fracture fracture porosit porosity y   , and the bulk matrix porosity   ), term, which describe the ability of the matrix to supply fluid to - and a matrix–fracture coupling term, the fractures.



Note No te that that the the perm permea eabi bili lity  ty     is not   the the perm permea eabi bili litty in the the frac fractu ture res, s, it is the

effective

permeability

of

the

formation , and that the porosities are bulk bul k porosi porositie ties s

The factor α is the block shape parameter that depends on the geometry and the characteristic shape of the matrix   –fissures system

    

Dual Porosity & Double Permeability Systems  Estimating parameters

how these two straight lines and their separation can be used to get estimates for  formation permeability, 

, matrix–fracture coupling, , and storativity ratio, 

The storativity ratio is estimated based on the separation of the two lines

   

Dual Porosity & Double Permeability Systems  Estimating parameters

how these two straight lines and their separation can be used to get estimates for  formation permeability, 

, matrix–fracture coupling, , and storativity ratio, 

an estimate for  is found based on either of the two times

   

Dual Porosity & Double Permeability Systems  Estimating parameters

   

4. Dual Porosity & Double Permeability Systems  Double Permeability    In

the double-permeability   (2K) model the  reservoir   consists   of   2   layers of  different

permeabilities, each of which may be perforated.    Crossflow

between the layers is proportional to the pressure difference between them.

When is a layered reservoir reservoir not a layered reservoir? When each layer has the same properties, in which case the behavior of the system will be the equivalent behavior of the summed interval 

   

Dual Porosity & Double Permeability Systems  Double Permeability

 In addition to the th e storativity ratio w and the interporosity interporosity flow coefficient coefficient l   , another coefficient is introduced: k is the ratio of the permeability-thickness product of the first layer to the total for both layers:

Usually the high permeability layer is considered as layer 1, so k will be close to 1 in DP system.

   

Dual Porosity & Double Permeability Systems  Double Permeability    At

early time there is no pressure difference

between the layers and the  system behaves as 2 homogeneous layers without crossflow, in infinite-acting radial flow, with the total kh of the 2 layers.    As

the most permeable layer produces more

rapidly than the less permeable layer,  a Dp develops

between

the

layers

and

crossflow begins to occur.   Eventually

the system behaves again as a

homogen homo geneous eous reserv reservoir oir,, with the total total kh and storativity and  storativity of   of  the 2  the 2 layers  layers    

Dual Porosity & Double Permeability Systems  Double Permeability

The heterogeneous dip in the derivative is now defined by 3 parameters:

The transitional dip is governed by w and l, which have the same effect as in the 2 f models models,, and k, which reduces the depth of the dip compared to k=1, which gives the dual-porosity pseudo-steady state solution.    

Dual Porosity & Double Permeability Systems  Double Permeability

The heterogeneous dip in the derivative is now defined by 3 parameters:

That is because if k=1 then k2h2=0, and the oil or gas in the low permeability layer, equivalent to the matrix blocks, can only be produced by entering the t he high-permeability layer layer,, equivalent to the fissure system. Not surprisingly it behaves like the dual-porosity model..  

Dual Porosity & Double Permeability Systems

 

Well Test Interpretation Model

 

5. Pressure Transient Analysis (PTA) - Numer Numerical ical models models Pressure Transient

Numerical models

57

     

Pressure re Transient Transient Analysis Analysis (PTA) - Numer Numerical ical models models Pressu –

 Typical ypical departures from the analytical model assumptions are: •   T Multiphase flow, •   non-Darcy flow •   and complex boundary configurations that are not easily generalized in an analytical model Such features can be addressed with a numerical model

Numerical models can provide considerable insight beyond that  possible from analytical models. models.

58

   

Pressure re Transient Transient Analysis Analysis (PTA) - Numer Numerical ical models models Pressu

Direct Problem Inverse Problem 2

     

Pressure re Transient Transient Analysis Analysis (PTA) - Numer Numerical ical models models Pressu  of  f  complexity  complexity,, the approach is to capture all When  sufficient  information supports  this  level  o •   known parameters in the simulation and use the resulting model to quantify what is not known. •   For For example example,, if transi transient ent data are acquired acquired that encompass encompass a ra radius dius of invest investiga igation tion that includes structural or stratigraphic barriers mapped from seismic data, capturing these in the numeric nume rical al model model may enable enable   quantif quantificat ication ion of are areal al per permeab meabilit ility y anis anisotr otropy opy that woul would d otherwise require interference testing to determine. determine.

Data from multiple wells acquired by  permanent monitors monitors are more easily interpreted with numerical simulation. Likewise , data acquired in complex wells employing multibranch and smart well

technologies require numerical simulation for rigorous analysis

 

Pressure re Transient Transient Analysis Analysis (PTA) - Numer Numerical ical models models Pressu •   In general numerical simulations are necessary in a number of contexts:

60

61

   

6. Pressure Transient Analysis (PTA) - Deco Deconvol nvolution ution Transient Analysis  The

superp superposi ositi tion on princ princip iple le was was intro introdu duced ced in connec connecti tion on with with the build buildup up test, test, and and

additional examples of application is  According to this principle, we can

the exprtwo-rate ess the test presand surethe resstep-rate ponse to test. any number of rate changes     oc occu curr rrin ing g at ti time mes s     in terms of the response in a sim imp ple drawdown test   ():

 

This continuous version of superposition is called convolution.

 )  from the known known pressure The inverse of convolution is deconvolution , means finding   (     and rate history   (  (    )  and  ′(  ′(    ). 63

   

Pressure re Transient Transient Analysis (PTA) - Deco Deconvol nvolution ution Pressu

it is not a new interpretation method   , but a new tool tool to process pressure and and more pressure data to interpret. rate data to obtain more pressure

64

    

Pressure re Transient Transient Analysis (PTA) - Deco Deconvol nvolution ution Pressu spiliting and lumping

It transforms variable rate and pressure data into initial constant rate pressure response equal 65 to the duration of the entire test  

Pressure re Transient Transient Analysis (PTA) - Deco Deconvol nvolution ution Pressu  In

principle, principle, by applying applying deconvolution, deconvolution, any

rate and pressure history can be analyzed using

the

methods

derived

for

the

drawdown test.  For

welll his histo tory ry wit with h uns unstab table le instance,   a wel

rates rat es or sev severa erall shor shortt shut shut-do -downs, wns, wher where e the late time responses will be masked by

short time fluctuations, fluctuations, can be analyzed for re res sponse nses

corre resp spo ondin nding g

to

the

to tottal

prod produc ucin ing g ti time me for for the the iden identi tifi fica cati tion on of  reservoir boundaries

 

 

Pressure re Transient Transient Analysis (PTA) - Deco Deconvol nvolution ution Pressu

66

67

 

Pressure re Transient Transient Analysis (PTA) - Deco Deconvol nvolution ution Pressu  One

would expect that most developments to come will be technology related, with more

powerful processing, higher graphics and higher amount of data available

Deconvolution

68

   

Well Test Design 1. Design and implementation of a well testing program can no longer be conducted under   standa sta ndard rd or tra tradit dition ional al rul rulee-ofof-thu thumb mb gui guidel deline ines. s.

   Incr Increa easi sing ngly ly

soph sophis isti tica cate ted d

 

reservoir

development and management practises,  

stringent safety requirements,

 

environmental concerns

   and

a greater need for cost efficiency

require that the  entire  testing  sequence  sequence,, from pro rog gram

desi esign

to

data

evalu lua ation,

be

conducted intelligently conducted  intelligently

   

Well Test Design keys to successful well testing are:

1. Proper test design,

2. correct handling handling of surface effluents, effluents, 3. high performance gauges, 4. flexible flexible downhole tools 5. and perforating systems, 6. wellsite validation 7. and comprehensive interpretation

   

Well Test Design keys to successful well testing are:

1. The importance importance of  clearly defined objectives  objectives and  and careful planning cannot be overstated. 2. Design of a well test includes development of  a dynamic measurement   sequence   and   selection of  hardware  hardware that  that can acquire data at the wellsite in a cost effective manner. manner. 3. Test design is best accomplished in a  software environment   where interpr interpreted eted openhole openhole logs, logs, production

optimisation

analysis,

well

perforation perfor ation and completion completion design and reservoir reservoir

test

interpretation

modules

are

all

simultaneously available to the analyst.

   

Well Test Design keys to successful well testing are:

1. Selecting the  instrumentation and equipment  for data acquisition is the final step of the test design process. 2. Surface Surface and downhol downhole e equipmen equipmentt   should should be vers versat atile ile to al allow low fo forr safe safe and and flexib flexible le

operations. Key factors to consider include;. Controlli olling ng the downho downhole le envir environme onment nt to mi minim nimise ise we wellb llbore ore sto storag ragee.  Contr 

ise rig tim time. e. Usi Using ng combin combined ed perfora perforatin ting g and testin testing g tec techni hnique quess to minim minimise

•

Choosing re relia liable ble dow downhol nholee rec record orders ers to ensu ensure re that that the the expe expect cted ed da data ta will will be re retr trie ieve ved d when when pull pullin ing g the the tool toolss out of hol hole. e.

•

Running ultra-high precision gauges when test obj bjeectives call for  deta detailed iled rese reservoir rvoir descr descripti iption on..

•

Se Sele leccting su surrfa face ce equi quipmen pmentt to sa safe fely ly ha hand ndlle exp xpec ectted rat atees and

•

 pressures. Enviro Env ironm nment entall ally y sou sound nd dis dispos posal al of prod produce uced d flu fluids ids..

   

Well Test Design Steps of  successful well testing are:

1. The

fir irs st

ste tep p

in test desig esign n

involves   di divid viding ing the re reser servo voir ir into vertical zones using zones using openhole logs and geological data. 2. The The type types s of well well or rese reserv rvoi oirr dat ata a

that th at sh shou ould ld be co coll llec ecte ted d

during

the

test

are

then

specified.. specified 3. The data to be collected collected drive the type of well test to test  to be run

   

Well Test Design Steps of  successful well testing are:

1. Once nce the the ty type pe of te test st is det eter ermi mine ned d, the the sequenc uence e chan changes ges in surf surface ace flow ra rate te   that seq should occur during the test are calculated. 2. The The chang changes es in flowr flowrat ate e and   their dur duratio ation n shou sh ould ld be re real alis isti tic c an and d pr prac acti tica call   so so they they interpretation patterns generate gener ate the  expected interpretation in the test data. 3. This

is

best

achieved

by

selecting

an

approp app ropriat riate e reservo reservoir ir model model and simulati simulating ng  sequence in advance the entire test test sequence    

Well Test Design Steps of  successful well testing are:

     

Well Test Design Steps of  successful well testing are: 1. Test seque sequenc nce e   simu simula lati tion on al allo lows ws the the ra rang nge e of poss possib ible le pressure and flow rate measurements to be explored. 2. Simulation Simulation a also lso he helps lps iso isolate late th the e  types  of  sensors capable of  measuring the expected ranges. 3. Diagno Diagnosti stic c   plots of simulated data should be examined to determine when essential features will appear, such as the well llbo bore re st stor orag age e ef effe fect cts, s, th the e du dura rati tion on of in infi fini nite te ac acti ting ng end of  we rad adia iall fl flo ow an and d the sta tarrt of to tota tall sys yste tem m resp spo onse in fi fis ssu sure red  d  systems.

4. The plots plots can a also lso he help lp anticipate  the  emergence  of  external

seal ale ed or pa parrti tial ally ly sea eale led d fa faul ults ts boundary   effects, including se and co const nstant ant pre pressu ssure re bo bound undari aries. es.

     

Well Test Design Steps of  successful well testing are: 1. The next step is tto o generate sensitivity plots  plots to  to determine the effects of reservoir parameters on the duration of different flow regimes.

 

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