WELL CONTROL COURSE SECTION A

SECTION A
KEY DEFINITIONS


Drilling Ahead






WHAT IS A KICK?

IT IS AN INFLUX OF FORMATION FLUID
THAT CAUSES THE WELL TO FLOW.


 
WHAT IS A BLOWOUT?

AN UNCONTROLLED EXIT OF THE FORMATION FLUIDS
AT THE SURFACE



 Hydrostatic Pressure

Hydro- means a fluid
Static- means at rest

Hydrostatic in the wellbore is from the mud

MUD HYDROSTATIC
         VERTECAL  WELL      

STANDERED FORMULA  WITH  FT., PPG AND PSI
MUD HYDROSTATIC  HP  = 0.052 X MUD WEIGHT X DEPTH
MUD GRADIANT   =  0.052  X MUD WEIGHT           PSI\FT.
Pressure (psi) = Mud Weight x .052 x TVD
Pressure Gradient (psi/ft) = Mud Weight, ppg x .052
Pressure Gradient (psi/ft) =Pressure, psi ¸ TVD, ft
Mud Weight, ppg = Pressure Gradient ¸ .052
Mud Weight (ppg) = Pressure ¸ TVD ¸ .052
TVD (ft) = Pressure (psi) ¸ Mud Weight (ppg) ¸ 0.052

FORMATION FLUID 
Fluid present in the pore space of the rock.
FORMATION PRESSURE
 
The pressure of the formation fluids.

  What is formation fluid pressure?
Formation Pressure: is the fluid pressure in the pore spaces of the formation.
BOTTOM HOLE PRESSURE 
IT  IS THE TOTAL  PRESSURES  EXERTED AT THE  BOTTOM  OF  THE WELL.
Balance
 
Mud Hydrostatic =Formation Pressure
Overbalance
 
Mud Hydrostatic >  Formation Pressure


Underbalance
  
Mud Hydrostatic <  Formation Pressure

 
WHAT IS WELL CONTROL?

1-PREVENTING A KICK
PRIMARY

2-SHUTTING IN THE WELL AFTER A KICK HAS BEEN TAKEN
SECONDARY
  
Primary control
Secondary Control
Blowout Preventers


 
WELL CONTROL CYCLE




HOW CAN KICKS HAPPEN?

Mud Hydrostatic and Formation Pressure
Always Remember that HP and FP are two opposite forces.
 

suker rod pump con't 2

Selection of the Proper Pumping Mode

The pumping mode of a sucker-rod pumping system is defined as the combination of pump size, polished-rod stroke length, pumping speed, and rod string design.
the optimum design is based on the value of lifting efficiencies and the one with the maximum ηlift is selected.
Maximizing the lifting efficiency coincides with the case of setting the polished rod power, PRHP, to be a minimum.
for a given hydraulic power
lifting efficiency and PRHP are inversely proportional.
A pumping system design made by this principle results in minimum operation cost and in a maximum of system efficiency.
If the best mode is selected, the energy input at the polished rod is only slightly greater than the pump’s hydraulic power, ensuring a lifting efficiency of over 94%.
The worst mode, on the other hand, requires almost three times as much energy as the best one for lifting the same amount of liquid from the same depth.


by increasing the pump size the attained maximum lifting efficiency values increase for all tapers.
Therefore, use of bigger plungers with correspondingly slower pumping speeds is always useful and results in lower energy requirements.
Also use of the heavier rod strings  increases the power requirement for smaller pump sizes.
OPTIMUM COUNTERBALANCING OF PUMPING UNITS

ideal counterbalance conditions are desired that can have many beneficial effects on the operation of the sucker-rod pumping system:
 Gearbox size can be reduced when compared to an unbalanced condition,
 The size of the required prime mover is smaller, and
   The smoother operation of a properly balanced speed reducer lowers maintenance costs and increases equipment life.
the mechanical Cyclic Load Factor (CLF). It can be calculated from the variation during the pumping cycle of the net torque on the reducer as the ratio of the root mean square and the average net torques:
These methods try to find the maximum counterbalance moment satisfying one of the following criteria:
The peak motor currents are equal during the up-, and downstroke,
 The peak net torques on the up-, and downstroke are equal,
 The required mechanical powers for the up-, and downstroke are equal, or
 A minimum of the cyclic load factor is achieved.
 
The CLF value valid for this case is greater than the minimum CLF achieved by the recommended optimization model.

PITFALLS IN ROD STRING DESIGN 


Rod string design aims at the determination of:
• The rod sizes to be used in the string,
• The lengths of the individual taper sections, and
• The rod material to be used.
The two basic problems in rod string design concern:
(1) how rod loads are calculated, and
(2) what principle to use for the determination of taper lengths.
At the time of design, rod loads are not known, and they also depend on the taper lengths that are about to be determined. Therefore, one has to rely on approximate calculations to find probable rod loads that will occur during pumping

Design Principles
Early rod string design methods utilized the simplifying assumption that the string was exposed to a simple tension loading. An examination of the rod loads during a complete pumping cycle, however, shows that the rod string is under a cyclic loading.
The nature of the loading is pulsating tension because the whole string is under tension at all times, but rod stress levels change for the up-, and the downstroke.
sucker-rod strings should be designed for fatigue endurance.
CONCLUSIONS


The pumping system’s energy efficiency depends primarily on the amount of downhole power losses.
  Maximum system efficiency is ensured by achieving a maximum of lifting efficiency.
 The proper selection of pumping mode can ensure maximum lifting efficiency and thus a most energy-efficient sucker-rod pumping system.
 Optimum counterbalancing of pumping units has many beneficial effects.
Minimizing the CLF is the preferred method for finding optimum counterbalanceconditions.
 Available rod string design procedures can have many pitfalls. Proper designs should provide a uniform fatigue loading of all rod taper sections.

SUCKER ROD PUMP con't

WAYS TO DECREASE PRODUCTION COSTS
FOR SUCKER-ROD PUMPING 
-roughly two-thirds of the producing oil wells are on this type of lift.
-To maximize profits from these wells in the ever-changing economic situation with rising costs of electric power, installation designs must ensure optimum conditions.
IMPROVING ENERGY EFFICIENCY 
energy losses both downhole and on the surface
      must be minimized.

1- Downhole Energy Losses

2- Surface Losses 







-The sources of down-hole energy losses in the
 
sucker-rod pumping system are :
 
-the pump, the rod string, and the fluid column.
 
The energy required for operating the polished
 
rod at the surface  is thus 
 
-the sum of the useful hydraulic work
 
performed by the pump and the downhole 
 
energy losses.
 
-This power is called the polished rod power or 
 
PRHP.
 
-The energy efficiency of the downhole 
 
components of the sucker-rod pumping system can
 
be known by the relative amount of energy
 
losses in the well.
 
This is called Lifting Efficiency.
 
 
 
Surface Losses 
 
 
mechanical energy losses Starting from the polished rod:

frictional losses arise in the stuffing box, in the pumping unit’s

structural bearings, in the speed reducer
 
(gearbox), and in the

 belt drive.
the electrical power taken by the motor is always greater than

 the mechanical power developed at the motor’s shaft.

The power losses in an electric motor are classified as mechanical

         and electrical.

Mechanical losses occur in the motor’s bearings
 
due to friction.

other losses include windage loss consumed by air surrounding the

 rotating parts.

an overall efficiency ηmot is used to represent
all losses in the

 motor, which, for average electric motors,
 
lies in the range of 85% to 93%.  
 
Optimum Energy Efficiency 
 
 
the energy efficiency is found from: 
 
 
Where : 
 
A more detailed formula
 
 
 


—the possible values of both the surface mechanical efficiency, ηmech, 
 
and the motor efficiency, ηmot, vary in

quite narrow ranges.

—At the same time, their values are not easy to improve upon; that is 
 
why. their effects on the system’s total efficiency are not very significant.

—On the other hand, lifting efficiency can be considered as the 
 
governing factor since it varies in a broad range depending on the pumping 
 
mode selected.

—Thus considerable improvements on the pumping system’s overall 
 
energy efficiency can only be realized by achieving a maximum of lifting 
 
efficiency.

—lifting efficiency mainly depends on the pumping mode selected (i.e.
 
the combination of plunger size, stroke length, pumping speed, and rod 
string design). 
 

subsurface safety valve




subsurface safety valve (video)

Surface Controlled Subsurface Safety Valves (SSSV)
subsurface-controlled subsurface safety valves