Presentation JB AG JCN JR 1
Kicks & blowouts A kick is an unexpected influx into a well of a formation fluid. Should this influx be uncontrolled... -- during its way from the bottom of the hole up in the open hole or -- when at surface, an internal or a surface blowout will occur. Blowout: is an incident where formation fluid flows out of the well or between formation layers after all the predefined technical well barriers or the activation of the same have failed. Presentation JB AG JCN JR 3
Kicks & blowouts occurrences When. - in exploration / appraisal drilling activities many geological and technical uncertainties leading to higher risks, - in workover activities risks of release of hydrocarbons during removal or installation of surface wellhead or BOP equipment. Presentation JB AG JCN JR 4
Source SINTEF - period 1980-2008 Presentation JB AG JCN JR 5
Kicks & blowouts occurrences some figures 34% are surface blowouts 66% are underground blowouts, 60% of occurrence while drilling, 27% while completion/wo, (8% during production, 5% others) Expenses associated with a blowout can reach several million of US$, Expenses for well control, costs for pollution control and containment measures, losses of facilities, penalties, fines... and tragedies, people can be killed. Presentation JB AG JCN JR 6
Blowouts. Surface blowout or blowouts Onshore or by mid-waters ( drilling wellheads with BOP s above waters) BOP s are easily accessible. Subsea blowouts Offshore, with subsea wellhead and BOP s ; BOP s are not easily accessible! Shallow gas blowouts A shallow gas blowout is difficult (or impossible ) to control; it may result in losses of lives and loss of the rig/platform; all effort must be made to divert the flow away from the rig: use of diverter and diverter lines Underground blowouts Uncontrolled flow of formation fluids from a high pressure zone into a lower pressure zone; the direction of fluid flow (up or downwards) is an important concern when choosing a control procedure. Presentation JB AG JCN JR 7
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KICKS & BLOWOUTS - Generalities Semi-submersible Actinia blowout shallow gas Vietnam - 1993 CADRE DRILLING HAZARDS: shallow gas Presentation JB AG JCN JR 9
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Nowadays blowouts are major catastrophic events Nowadays blowouts are major catastrophic events Presentation JB AG JCN JR 12
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BLOWOUTS & Well Engineering Studies OVERVIEW OF MAIN WELL ENGINEERING STUDIES AND TASKS for. Environment studies Max expected surface pressure and well data collection WP of well control equipment,. Mud studies & program Drilling engineering Pore pressure prediction Fracture pressure prediction Well completion studies * Cement: for. studies & program Well control procedures, Internal blowout prevention Casing., wellhead design WELL DRILLING PROGRAMME Well test program Well abandon: program Casing setting depth selection Rock mechanic studies Drilling for. bit program Well control procedures, Internal blowout prevention Drillstring. design Contingency plan (incld. BOCP) Drilling progress curve Well profile (deviation, hole & casing size) Well Collision Avoidance Rig sizing and selection Cost / budget - AFE ** * complulsory for developt well ** Authorisation For Expenditures Presentation JB AG JCN JR 14
BLOWOUTS & Well Engineering Studies Mud studies & program Drilling engineering First safety barrier OVERVIEW OF MAIN WELL ENGINEERING STUDIES Impact AND of TASKS mud type on kick detection Environment studies hydrates and well data collection Pore pressure prediction Fracture pressure prediction Well completion studies * Casing setting depth selection Rock mechanic studies Well profile (deviation, hole & casing size) Cement: studies & program Casing, wellhead design Drilling bit program Drillstring design Rig sizing and selection Cement = one safety barrier. WELL DRILLING PROGRAMME Well test program Casing: burst resistance Well abandon: program. Contingency plan (incld. BOCP) Drilling progress curve Selection of BOP WP. Cost / budget - AFE ** * complulsory for developt well ** Authorisation For Expenditures Presentation JB AG JCN JR 15
BLOWOUTS & Well Engineering Studies OVERVIEW OF MAIN WELL ENGINEERING STUDIES AND TASKS Environment studies and well data collection Mud studies & program Drilling engineering Pore pressure prediction Fracture pressure prediction Well completion studies * Casing setting depth selection Rock mechanic studies Cement: studies & program Casing, wellhead design All BOP data are needed (capping,.) Drilling bit program Drillstring design WELL DRILLING PROGRAMME Well test program Well abandon: program Contingency plan (incld. BOCP) Drilling progress curve Well profile (deviation, hole & casing size) Rig sizing and selection Cost / budget - AFE ** * complulsory for developt well ** Authorisation For Expenditures Presentation JB AG JCN JR 16
Typical circuit of the influx while controlling the well Drillpipe In-hole Pipe rams closed Influx (kick) returns In the annulus Presentation JB AG JCN JR 17
Well shut-in: pressures in the well Surface pressure 0 psi 6 864 psi 0 critical casing press.? 6 000 ft Casing shoe critical EMW 33 ppg! 12 000 ft Gas influx Fracturation will occur in open hole Bottom Hole Pressure 6 864 psi 10 296 psi 13 728 psi Equivalent Mud Density at bottom 11 ppg 16.5 ppg 22 ppg! Presentation JB AG JCN JR 20
Well kick control: principles (1/2) Initial pressure regimes (well shut in) DP pressure = Pt1 Initial MW = di (known) Annulus press. = Pa1 Pt1 = reference pressure indication for calculation D = well vertical depth, Coeff. = depends on units, di > da Initial mud + Influx = da ( unknown ) P = coeff *D * di + Pt1 = P =coeff * D * da + Pa1 Formation pore press. ( > coeff* D*di ) Presentation JB AG JCN JR 22
Well kick control: principles (2/2) Circulating pressure for well control = P1 = Pc1 * + Pt1 + S Annulus press. Pa = Pa1 + S Note: circulating pressure to be maintained if no change of the initial MW, di choke Pressure regimes (starting well control) * Pc1 = circulating pressure measured at reduced flow rate P = coeff *D * di + Pt 1 + S = P= coeff * D * da + Pa1+ S Formation pore press. Presentation JB AG JCN JR 23
Drilling conditions Well Control Procedures in progress BOP BOP closed P ann = 0 P ann P ann P ann MAASP max MAASP max Ps max critical P frac P frac critical PR PR PR PR new mud weight Presentation JB AG JCN JR 24
WELL CONTROL: Principle & Methods Important data required prior initiating well control procedures: - drillstring geometry - hole geometry - mud density, - pump flow rate per stroke - pressure losses at low flow rates (kill-flow rates) for different well control mud circuits - fracturation pressure & weak points in the open hole - Surface to bit time at kill rate (in stroke and minutes) - Bit to surface time at kill rate (in stroke and minutes) - Maximum Allowable Annular Surface Pressure (MAASP) - Formula for calculating the kill mud density - Formula for calculating circulation pressures due to the effect of heavier mud WELL CONTROL SHEET Presentation JB AG JCN JR 25
The basic principle of well-control methods is to keep the bottomhole pressure (BHP) constant while circulating the fluid influx out of the well. The simplest method of doing this is to control the drillpipe pressure by running the pump at a constant rate and controlling the pressure by regulating the choke on the choke manifold Presentation JB AG JCN JR 28
SAFETY BARRIERS while drilling and workover operations. Associated well control barriers include drilling fluid, casing, cement, casing shoes, wellhead seals, blowout preventers (BOPs) and the interaction among all of them. Drilling and workover operations shall at all times be conducted with two barriers on each internal and external leak path, capable of operating independently and simultaneously and isolating potential hydrocarbon reservoir from the surface Two barriers are considered as independent if any incident considered in risk analysis cannot induce the loss of the two barriers simultaneously. Source / Illustrations: TOTAL Presentation JB AG JCN JR 29
Safety barriers External leak path WH seals Internal leak path BOP s WH seals mud mud * cement mud HC Drill pipe Cem. Equipt. Source / Illustrations: TOTAL Inside DP BOP Presentation Presentation JB AG JCN JB JR - 30
Safety barriers External Note: leak path Internal leak path When drilling deepwater wells, the percentage BOP s of drilling time WH seals rotating on bottom while drilling new hole is sometimes mud less than 20%. mud * WH seals It is important to understand that barriers can be impacted significantly during all well operations, not just drilling. cement mud HC Drill pipe Cem. Equipt. Source / Illustrations: TOTAL Inside DP BOP Presentation JB AG JCN JR 31
Filters for prevention Filters for protection Causes Loss of well control Swabbing Pore Press prediction Bad cementing. Engineering Procedures Equipment Personnel Consequences Soil instability Well collision Loss of rig stability Loss of well integrity Punch through Bad weather. Blowout Polution control equipt. Capping equipt. Pollution Fire, explosion Damages to wellheads. Presentation JB AG JCN JR 33
Drilling hazards blowout prevention -. before drilling operations = engineering studies,. Refer to casing architecture and casing design versus evaluation of formation pore pressure / evaluation of formation fracturation pressure / evaluation of maxi. acceptable surface pressure and set up of the proper BOP equipment. -. while drilling = procedures. permanent monitoring of mud volumes in circulation (gains or losses),. permanent monitoring of mud weight (and mud viscosity),. permanent monitoring of ROP: drilling breaks,. tests (and maintenance) well control equipment incld. BOP, choke manifold, inside-bop, (tests after each new installation and on regular basis (e.g. each week)),. training of rig-crews: regular kick drills to test rig-crews preparedness,. calculations for immediate application of pre-set procedures. Presentation JB AG JCN JR 35
Drilling hazards blowout prevention (contd.) - while tripping = procedures.. permanent monitoring of mud filling the hole when RIH or POOH,. training of rig-crews: regular kick drills to test rig-crews preparedness,. calculations for immediate application of pre-set procedures. Well control procedures imply an intensive use of the BOP. If a BOP failure occurs then the kick will be uncontrolled leading/meaning to/a blowout. Presentation JB AG JCN JR 36
Alerts or warnings - drilling breaks, - increase of mud level in the active mud tanks, - gas-cut mud or gas/oil shows, - changes in mud properties (chlorides, ), changes of shale densities, - light influx when circulation is stopped, - uncorrect filling of the hole while pulling-out-of hole the drillstring, - decrease in the mud pump discharge pressure. - information provided by MWD,LWD,PWD (gamma ray, resistivity, density, neutron, sonic). WHEN WARNING SIGNS ARISE, PERFORM THOROUGH ASSESSMENTS BEFORE MOVING ON. Presentation JB AG JCN JR 37
Overpressure detection Gas Readings Increasing ROP Source: TOTAL Presentation JB AG JCN JR 38
Other precautions.. - when drilling with oil-based mud, gas remains in solution as the fluid is circulated up the hole until the bubble point is reached; then a violent kick occurs as gas bursts out of solution in the upper portion of the hole (casing or drilling riser), - When drilling (HP/HT wells) some supercharging/balloning & well breathing effects must be detected to avoid confusion with a kick - When drilling high deviated wells (near horizontal), detection and behaviour of gas bubbles are of important concern. REMEMBER The probability of a well control problem may be low, but the consequences are high enough to justify considering all causes, warnings... Presentation JB AG JCN JR 39
Immediate corrective actions - CLOSE THE WELL: implementation by the driller of the well shut-in procedures, When applicable (kick during tripping): whenever possible, attempt to run the drillstring down hole, (stripping), - As soon as possible, implementation of well kick control method and procedures to evacuate the influx from the well bore, Ultime method: If necessary and possible, squeeze/bullhead the influx back into the formation. If an unforeseeable event occurs or if a BOP equipment failure occurs a blowout situation will be imminent; then activate immediately the Blowout Contingency Plan Presentation JB AG JCN JR 40
WELL CONTROL: Principle & Methods Some concerns about offshore well control procedures Conventional well control procedures applicable for land or shallow waters. Early kick detection: is necessary - to minimize the influx volume, and - because of the large expansion of gas in the drilling riser that can occur. Notes: - BOP positioned at mudline sometimes nearer to well TD than to surface! - Managed Pressure Drilling (MPD) techniques (equipment & procedures) can provide a precise and real time measurements for early kick-loss detection. Space out: the Driller must quickly determine the space out of the drillstring for closing rams. position of BOP elements (e.g. shear rams) relative to rig floor must be displayed on driller s panel. Hang-off procedures:?? 43 Presentation JB AG JCN JR 43
WELL CONTROL: Principle & Methods Some concerns about offshore well control procedures (contd.) Shut-In procedures: Soft or Hard shut-in procedures can be implemented. Whenever the well is shut-in, gas in the riser shall be considered as the first priority and diverted directly overboard. Driller s versus Wait and weight kill method:?? Riser margin: it is recommended (when applicable or if relevant ) to include a riser margin in the mud weight. Presentation JB AG JCN JR 44
WELL CONTROL: Principle & Methods Some concerns about offshore well control procedures (contd.) Long kill and choke lines: pressures losses in these lines ** are high even at low circulation rates; consequently MAASP is reduced. It is compulsory to measure all pressure losses at reduced flow rates through different sections of the mud flow paths. ( ** Potential use of choke and kill lines in well control circulation). BOP s: High shear rams capacity must be assessed due to high drillpipe specifications (grade and size). BOP response time: this is a key issue; All systems to operate the BOP s in emergency situations must be tested in due time. For offshore operations, special training courses for Rig Personnel and Office Engineers must be given. Presentation JB AG JCN JR 45
Main calculations. Maximum annulus pressure well shut-in and filled with gas == > to evaluate well equipment strength. MAASP * == > to avoid risk of fracturing the formation at the weak zone ( * Maximum Allowable Annulus Surface Pressure). Maximum casing pressure during the circulation of a gas kick with the initial mud weight == > evaluation of well equipment strength and maxi allowable kick volume. Maximum pressure at weak zone during the circulation of a gas kick with the initial mud weight = = > evaluation of maxi allowable kick volume at shut-in. Maximum allowable kick volume at shut-in == > to avoid risk of fracturing the formation at the weak zone. Quick evaluation of the influx pressure gradient = mud pressure gradient + (Pt1 Pa1) / h ( h = initial height of the influx in the annulus) Presentation JB AG JCN JR 50
Underground blowout flow outside the wellhead Catastrophic situation weak point Bad cementing job or, Weak point(s) in the openhole Initial too large influx, or driller s mishandling Presentation JB AG JCN JR 52
DRILLING HAZARDS Lusi mud flow Indonesia (may 2006) Source: photos M.Tingay and Channel 9, may 2007 Presentation JB AG JCN JR 53
Results / consequences of. - Engineering works? (questionable casing-setting-depth design? ) - Operational human error? - External events? Presentation JB AG JCN JR 54
Underground blowout (internal blowout) Tubing failure (leak) weak point HP zone loss zone or depleted zone! packer Presentation JB AG JCN JR 55
Underground blowout (internal blowout) Such blowouts are catastrophic as they can lead to - the loss of the well, - new hazards when drilling wells in the vicinity, - subsurface / internal contamination between reservoir layers,. Precaution first preventing measures: - perform engineering tasks === > casing point selection, - update blowout prevention data sheets, - perform regularly kick drills, - evaluate, as necessary, cement bond behind casing after cementing job, - check casing/tubing integrity tests as necessary ( before DST), Presentation JB AG JCN JR 56
BLOWOUT - WELL CONTROL Whenever an exploration well is planned, the drilling team must prepare a Blowout Contingency Plan. Such plan, to list actions to be taken for the safeguard of the People, the environment and the assets; to list all updated contacts for assistance. A special team blowout task force is mobilised with all competencies (geoscientist, reservoir, drilling, logistics, contract Engineers) as soon as possible. At the same time - relief well(s) will be engineered; rig(s), special directional drilling equipment, pumping means will be located and/or mobilized - fire-fighters Specialists (*) will be mobilised together with their equipment for well killing and/or well capping ( * Wild Well Control, Boots & Coots, Cudd, West, John Wright Co, Red Adair) Presentation JB AG JCN JR 59
ONSHORE / OFFSHORE BLOWOUTS RELIEF WELLS Source / Illustrations: Wild Well control Presentation JB AG JCN JR 60
relief well drilled directionally Blowout on the WP Surface wellhead Floating rig Subsea wellhead 1000 to 1500 m Blowout well Relief well Source / illustration: Books from IFP and Chambre Syndicale de la Recherche et de la Production du Pétrole et du gaz naturel reservoir Presentation JB AG JCN JR 61
ONSHORE BLOWOUT Well capping Source / Illustrations: Wild Well control Presentation JB AG JCN JR 62
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Source / Illustrations: Wild Well control Presentation JB AG JCN JR 64
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Source / Illustrations: Wild Well control Presentation JB AG JCN JR 69
Source / Illustrations: Wild Well control Presentation JB AG JCN JR 70
Slides were prepared for presentation and information to Students of Schools and Universities only. References Slides presented were prepared with illustrations from the following referenced documents: - API Standards and Recommended Practices, - Neal J. Adams, Drilling Engineering, PennWell Books, Tulsa, Oklahoma, 1985, - (Halliburton) - Petroleum Well Construction J Willey & Sons - Miscellaneous books from Chambre Syndicale de la Recherche et de la Production du Pétrole et du gaz naturel - IFP Drilling data handbook - Miscellaneous documentation from TOTAL Drilling Division - Halliburton Completion Services - Miscellaneous books from IFP - Leading Edge Advantage Ltd (Under Balance Drilling). - Miscellaneous documentation from web-sites: O&GJ, World Oil, SPE - Transocean, Saipem, Pride Drilling Contractors - Baker Hughes, Schlumberger, Weatherford, Wild Well Control Service Companies - Cameron, Hydril, Companies. Presentation JB AG JCN JR 71