How to Predict Formation Pressure Prior to Drilling

Formation pressure can be predicted from 3 information sources prior to drilling as follows;

1. Seismic Data

Seismic is the way to predict formation types by sending sound waves that penetrate into subsurface structure. Then, sound waves reflected back from formation are recorded as raw data. Geologists are able to predict geological structures and potential pressured zoned by interpreting the sound waves. With current 3D seismic modeling, the pressured zones are accurately predicted.

2. Geological Data

Geological information demonstrates condition that possibly causes abnormal pressure zones. The subsurface structures associated with abnormal pressure characteristics are anticlines, charged zones, depleted zones, faults, massive shale and Salt formations.

Anticlines: Anticlines is the geological structure that looks like a dome. Anticlines with cap rock on top are good geological structure because hydrocarbon can possibly trapped below it. While drilling into top structure of anticlines, abnormal pressured zones are expected.

Charged Zones: Charged zones are shallow formations that have pressure connectivity from abnormal pressure zones below. Because of upward movement of reservoir fluid from deeper zones, charged zones are normally abnormal pressure. Charge zones can occur by nature or man-made. Currently, new geophysical methodologies can be applied for find where the charged zones are prior to drilling.

Depleted Zones: Depleted zones are formations that have less pressure than original formation pressure because some formation fluid has been produced. Using historical data in conjunction with geological techniques can determine where the possibly depleted zones are.

Faults: Because each fault block may has different pressure gradient, while drilling across a fault, drilling problem associated with pressure such as well control problem or lost circulation may possibly happen.

Massive Shale: Shale is non permeable formation therefore it restricts movement of formation fluid. When a lot of overburden formation layers are accumulated over massive shale, shale is compacted and reservoir fluid naturally tries to come out from the pore space. However, shale is impermeable and it does not allowed pore fluid to come out therefore formation pressure caused by formation fluid becomes over pressured.

Salt Formations: There are several parts of the world where pure and thick layers of salt are present. Typically, salt formations are laterally and upwards forced causing salt domes. Because salt is impermeable, it does not allow formation fluid pass through it; therefore, formations below a salt formation are normally abnormal pressure.

3. Historical Data

The historical data from adjacent area is good information for prediction formation pressure. Historical information can be obtained from formation pressure, mud logging reports, drilling reports, drilling fluid reports, Logging While Drilling (LWD), Pressure While Drilling (PWD), etc.
Reference book: Well Control Books

How to Assess Material Requirements for Drilling Operation

Drilling supervisors must be responsible for assessing material requirements for the drilling operation at a drilling rig. There are several following information that can help to assess material requirement in both short time (less than 48 hrs) and long time (next 3-5 day).

1. Drilling Operation Instruction: The drilling operation instruction is guidance for what operations will be happening in the future. Therefore, it will give people at the rig some ideas regarding what people will be needed.

2. Drilling Operation Meeting: The operation meeting is conducted everyday in order to discuss the forward plan among team members such as drilling supervisors, a drilling contractor and service companies. This meeting helps all parties at the rig to understand what drilling activities will be performed and when the operation requires the material perform jobs.

3. Forward plan sheet: The forward plan sheet contains all actions from demobilization to completion of the drilling program. It assists supervisors on the rig to estimate time for upcoming operations. Mostly, it is utilized for assessing the long time (next 3-5 days) material and people requirement.

4. Area on the rig: Operation supervisors must fully understand about available space of the rig because it is a constraint about how much equipment can be store on the rig. For instant, if the rig has small area, small set of equipment must be frequently ordered. On the other hand, if the rig area is big, a lot of drilling tools can be requested and kept on the rig.

5. Logistics: It is very important to know how the logistics work each area because it will help personnel on the rig know how long the equipment will be transferred from a wear house to a location after issuing the material.

6. Contact Warehouse: After all required materials are assessed, drilling supervisors and a material man must contact a warehouse in order to discuss with them about what the required materials are and when they should be at the rig site.

Normally, material requirement plan must be revised everyday because sometimes drilling operation is not ongoing as plan. Therefore, some equipment must be delayed or some special equipment must be urgently requested for specific drilling operation.

Oil Field Abbreviation Mostly Used in the Rig

This is may not relate to drilling formula but it may be good for new people to know about oil field abbreviations. If you have more than what I have, please feel free to add more by putting in the blog comment.

ACF – Annular Capacity Factor

AV – Annular Velocity

BF – Buoyancy Factor

BHA – Bottom Hole Assembly

BHP – Bottom Hole Pressure

BOP – Blow Out Preventor

BOPE – Blow Out Preventer Equipment

BPUTS – Bring Pumps Up To Speed

CC – Circulate and Condition mud

CLF – Choke Line Friction

CMW – Current Mud Weight

CP – Casing Pressure

DC – Drill Collar

Dh – Diameter of hole in inches

DP – Drill Pipe

DPP – Drill Pipe Pressure

ECD – Equivilant Circulating Density

EOB – End of Build

ESP – Estimated Stuck Point or Electical Submersible Pump

FCP – Final Circulating Pressure

FD – Fluid Density

FIT – formation integrity test

FOSV – Full Opening Safety Valve

FP – Formation Pressure

FrP – Friction Pressure

FV – Funnel Viscosity

GPM – Gallons Per Minute

HHP – Hydraulic Horse Power

HP – Hydrostatic Pressure

IBOP – Inside Blow Out Preventer

ICP – Initial Circulating Pressure

ISICP – Initial Shut-in Casing Pressure

KLF – Kill Line Friction

KMW – Kill Mud Weight

KOP – Kick Off Point

Lbs. – Pounds

LC – Lost Circulation

LCM – Lost Circulation Material

Len – Length in feet

LOT – Leak Off Test

MAASP – Maximum Allowable Annular Surface Pressure

MASP – Maximum Anticipated Surface Pressure

MD – Measured Depth

MGS – Mud Gas Separator

MI – Mud Increment

MISICP – Maximum Initial Shut-in Casing Pressure

MOP – Margin of Over Pull

MW – Mud Weight in ppg

NP – Neutral Point

OBM – Oil Based Mud

OMW – Original Mud Weight

OPT – Optimum

PG – Pressure Gradient

PI – Pressure Increment

POH – Pull Out Hole

PP – Pore Pressure

PPG – Pounds Per Gallon

RIH – Run In Hole

ROH – Run Out Of Hole

RPM – Rounds Per Minute

RSS- Rotary Steerible System

SCR – Slow Circulating Rate

SG – Specific Gravity

SICP – Shut-in Casing Pressure

SIDPP – Shut-in Drill Pipe Pressure

SOBM – Synthetic Oil Based Mud

SP – Surface Pressure

SPM – Strokes Per Minute

SPM Valve – Side Pocket Mandrel Valve

SPR – Slow Pump Rate

TDS – Top Drive System

TIH – Trip In Hole

TOC – Top Of Cement

TOF – Top Of Fish

TOH or TOOH – Trip Out Of Hole

TOL – Top Of Liner

TVD – True Vertical Depth

WL – Water Loss or Wire Line

WOB – Weight On Bit

WOC – Wait On Cement

WOO – Wait On Orders

WOW – Wait On Weather

YP – Yield Point