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PROPOSAL       FOR TACKLING THE OIL LEAKAGE FROM THE DEEPWATER HORIZON FIELD                                              ...
2. Concept descriptionSketch 1 shows the balloon over the well head. From the sketch the following can be seen.    1. The ...
Sketch 1. Balloon anchored above the well headAs was mentioned above the balloon will be open at its bottom and the bottom...
that at the top of the balloon. This will happen, of course, until the whole volume inside theballoon will be captured by ...
3. Performing some calculationsThe following assumptions are madeWater depth (h):                                         ...
Where uc is the speed of the flow inside the flexible pipe and we assume pressure at the seasurface zero and reference poi...
buoyancy forces, or by pumping out the oil from the balloon with a flow rate higher than theflow rate of the well.There ar...
Table 1. Simple calculations on the concept based on imaginary data Assumed input information z=                          ...
4. Concluding remarksA proposal is made which may give a solution of how to trap the oil coming out of the oil head ofthe ...
Sketch 3. A way to realize the proposed concept with a dome instead of a balloon.Offshore Energy Systems SA, 48 Karaoli & ...
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BP Deep Horizon Oil Field. A proposal for tackling the oil leakage at the Gulf of Mexico oil field

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This present proposal was submitted to BP on 15-5-2010 during the crisis in the Gulf of Mexico.

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Transcript of "BP Deep Horizon Oil Field. A proposal for tackling the oil leakage at the Gulf of Mexico oil field"

  1. 1. PROPOSAL FOR TACKLING THE OIL LEAKAGE FROM THE DEEPWATER HORIZON FIELD By: Antonis Daskalakis, Offshore Engineer, Phd, Offshore Energy Systems SA, Greece 14-05-2010 1. IntroductionThis present report contains a proposal for tackling the oil leakage from the well head of theGulf of Mexico oil field of BP.The idea may be wrong but there is no time for more analysis from my part. It is better that theconcept presented here will be examined by more experienced and more knowledgeableengineers of BP instead of waiting to prove everything myself, just to publish a paper after thedisaster. There is no time left for the environment.The idea contained here came to me since I am working on a project for compressed air storagein big balloons in the sea bottom as intermediate energy storage produced by renewable energysources (wave, wind).In short the concept is to lower a big balloon over the well head to capture the oil coming outand pump it to the surface to a tanker or other proper storage facility.The balloon will be open at its bottom, it will be covered by a strong net which will be attachedto a steel structure of proper design and weight which will be driven to seat on the sea bottomover the well head.The balloon is not meant to seal the well head as this will be difficult or unachievable due tohigh pressures (and temperatures) of the oil coming out from the well head. However I believe itis not required to seal the well, as it is explained below, in order to capture the oil.The balloon will stand above the well head to a short distance (gap), held there by the net whichis attached to the steel structure, seated on the bottom.The oil will be pumped to the surface through a flexible pipe held upright by floaters properlydistributed along it. The pumping can be done naturally due to the difference of densitiesbetween water and oil, or it may be helped by a pumping arrangement on the storage facility.Offshore Energy Systems SA, 48 Karaoli & Dimitriou str. 15232 Halandri/Athens GreeceTel.: +302106775003, Fax: +302106812770, e-mail: daskalakis@martech.gr Page 1
  2. 2. 2. Concept descriptionSketch 1 shows the balloon over the well head. From the sketch the following can be seen. 1. The steel structure which will anchor the balloon over the well head. The steel structure is a circular construction which partially penetrates the soil mainly for increased holding capacity. 2. The balloon is made by strong polyethylene or other proper material. The dimensions of the balloon are to be determined by the data of the well as can be discussed later. 3. The net which undertakes the buoyancy forces in a uniform manner, as well as current forces acted upon the balloon and transfer to the steel structure. 4. Sinker weights which will hold the balloon over the steel structure even if there is no pressure inside the balloon and it is in a slack condition. The sinker weights can also be additionally anchored on the sea bottom providing additional support to the balloon. However the sinker weights can also act as shock absorbers in case of a blasting or a rapid change of pressure inside the balloon. 5. The flexible pipe which will lead the oil to the surface. The pipe is in fact a flexible riser and there is great experience in the industry for the design, construction and installation of such systems. 6. The floaters which will keep the pipe in upright position and will take its weight uniformly avoiding overstresses.Offshore Energy Systems SA, 48 Karaoli & Dimitriou str. 15232 Halandri/Athens GreeceTel.: +302106775003, Fax: +302106812770, e-mail: daskalakis@martech.gr Page 2
  3. 3. Sketch 1. Balloon anchored above the well headAs was mentioned above the balloon will be open at its bottom and the bottom opening will beallowed to be in a distance from the steel structure so that there is a gap between well head andthe balloon opening.Therefore there is no sealing of the well head. As the oil is coming out from the well, as an oilbeam with high speed (defined by the reservoir characteristics), it will come inside the balloonlike a squirt.The total pressure of the beam at the well head will be equal to the pressure of the water at thesea bottom (for 1500 m water depth approximately 150 bar).Since the speed of the oil beam, I assume, will be high the static pressure due to Bernoulli willbe less than the surrounding water static pressure and therefore there will be no leakage of oilfrom the gap between the balloon and the sea bottom. In this way the whole amount of oilcoming out from the well will be led inside the balloon.As the oil is lighter than water it will be gathered in the upper part of the balloon which willgradually be “inflated” since the water pressure at the bottom of oil chamber will be higher thanOffshore Energy Systems SA, 48 Karaoli & Dimitriou str. 15232 Halandri/Athens GreeceTel.: +302106775003, Fax: +302106812770, e-mail: daskalakis@martech.gr Page 3
  4. 4. that at the top of the balloon. This will happen, of course, until the whole volume inside theballoon will be captured by oil. After that the oil will again be led to the sea.If however the oil from the balloon can be pumped out to the sea surface, in the same pace as itcomes out from the well, there will be a continuous flow of oil from the well head to the seasurface without leakage to the sea. Can this be done?Paying attention to sketch 2 the oil from the oil chamber will be led to the flexible pipe (riser).Since the water pressure at the bottom of the oil chamber is higher than the oil inside theflexible pipe the oil will be naturally pumped out of the balloon to the surface.The real question however is if the oil flow rate inside the pipe, driven by the natural differentialpressure can be equal to the flow rate from the well. If it is less, then the balloon will begradually filled with oil and oil will leak to the sea from the open bottom of the balloon. If it ismore then, water will reach the surface and oil pumping will be interrupted, while the balloonwill become slack.In the following, some calculations will be performed based on imaginary data in order toillustrate the way one can deal with the problem and the sizing of the proposed system.Sketch 2. Schematic functioning of the proposed set upOffshore Energy Systems SA, 48 Karaoli & Dimitriou str. 15232 Halandri/Athens GreeceTel.: +302106775003, Fax: +302106812770, e-mail: daskalakis@martech.gr Page 4
  5. 5. 3. Performing some calculationsThe following assumptions are madeWater depth (h): 1500 mReservoir pressure (Pr): 600 barDepth of reservoir (from the sea bottom) (z): 4000 mOil density (ρο): 850 Kg/m3Water density (ρw): 1025 Kg/m3Based on this information and Bernoulli’s equation we have (1)Where ur is the speed of the oil beam at the wellhead and the other symbols have beenexplained before. This is a very simplified calculation it assumes a single phase oil media, no gascontent or other formations. Petroleum engineers with knowledge of the reservoircharacteristics can perform exact calculations).In the above we assumed that the pressure at the wellhead will be equal to the water pressureat the well head (sea bottom). This is very important and makes the difference between a sealedchamber and a not sealed one as it is presented here.From this equation it is possible to calculate the speed of the oil beam at the well head.Naturally from this calculation one can also calculate the height of the squirt inside the balloon.I suppose this height is known to the engineers of BP from observations through an ROV or fromcalculations.The size of the balloon should be such so as to allow the unobstructed development of thesquirt to avoid forces acting on the internal surface of the balloon. If it is too high one couldthing of a cylindrical shape of the balloon instead of the spherical one we show in our sketches.From the speed and the known diameter of the well one can calculate the flow rate of oilcoming out from the well. This information is also available to the engineers of BP, but not tome. For our demonstrative calculations we assume this diameter to be 100 mm.From the balloon the oil is pressed to flow inside the flexible pipe due to the water pressure atthe bottom of the oil chamber. Bernoulli’s equation will then give: (2)Offshore Energy Systems SA, 48 Karaoli & Dimitriou str. 15232 Halandri/Athens GreeceTel.: +302106775003, Fax: +302106812770, e-mail: daskalakis@martech.gr Page 5
  6. 6. Where uc is the speed of the flow inside the flexible pipe and we assume pressure at the seasurface zero and reference point at the sea bottom.Table 1 has been included which give the assumptions made before and provide the simplecalculations using the above two equations.The following are calculated: • The speed of flow inside the well • The flow rate with the assumed well diameter • The flow speed inside the flexible pipeTable also gives the ratio of the speed of oil flow inside the well and inside the flexible pipe. Thesquare root of this ratio gives the ratio of the diameters of the two pipes (diameter of flexiblepipe over diameter of well) so that the two flows are equal.In sizing the flexible pipe one can increase its diameter and incorporate a valve at the seasurface to control the flow rate. The control should be in such a way as to keep the balloon sayhalf filled (or less). In this way the balloon acts as a buffer area and its size should be such as toprovide flexibility in the whole operation and safety limits to absorb unexpected deviations ofthe flow rate.Furthermore with an assumed diameter of the balloon its volume is calculated and anestimation of the time required to fill the balloon with oil is given (based on the calculated flowrate of the well). This time is important at the first installation of the whole set up. Long timewill allow the steel structure to be settled on the sea bottom before buoyancy forces willdevelop inside the balloon making difficult the job. Sinker weights can also help in this transientperiod. Later during normal operation is an indication of the size of the buffer area and thecontrollability of this operation.In case the balloon is partially or totally filled with oil a buoyancy force will be developed on theballoon due to the difference of the densities of oil and water. This is calculated and given intable 1 for the totally filled balloon.This has to be taken into account in order to calculate the required dead weights to keep theballoon on the sea bottom.However the required weight should be more than taking the buoyancy. On the balloon forceswill be acting, mainly due to currents. These forces have to be calculated based on currentspeed measurements and the projected area of the balloon. There must be excess weight toprovide holding capacity of the steel structure to horizontal forces. This is the reason behind thedesign of the steel structure which is meant to penetrate the soil increasing its holding capacity.This can be done before an oil chamber develops inside the balloon, when there are noOffshore Energy Systems SA, 48 Karaoli & Dimitriou str. 15232 Halandri/Athens GreeceTel.: +302106775003, Fax: +302106812770, e-mail: daskalakis@martech.gr Page 6
  7. 7. buoyancy forces, or by pumping out the oil from the balloon with a flow rate higher than theflow rate of the well.There are also some other problems and design parameters to be taken into account:The first is oil temperature which is not known to me and what the properties of the material ofthe balloon should be to withstand it. It is believed that the low water temperatures at thedepth of 1500 meters (4 oC ?) will help in cooling the upcoming oil. Temperature also is asignificant parameter in the formation of hydrates as it is discussed in the following. It istherefore a matter to be studied by experts in the field.Second is the case of a blasting from the well. I do not have information on the reservoircharacteristics, I do not know the probability of such an event and its nature. If such a case isprobable then one has to foresee the effects and ways to absorb it.In the present concept a number of flexibilities are incorporated which give absorbingcharacteristics to the system. These characteristics include: 1. The elastic structure of the balloon. A rigid construction cannot behave correctly in a case of a blast. 2. The uniform distribution of pressures inside and outside the balloon and the fact that the differential pressure is kept low during normal operation. 3. The sinker weights which will act as shock absorbers in case of a blast. This absorbing capability can be enhanced by choosing the material of the ropes which hang the weights.A third problem is the formation of hydrates. The conditions for such a formation have to bestudied carefully by experts on the field. It may be possible the whole set up to be designed in away to avoid this formation. It can be possible to use inhibitors like ethanol, methanol or otherswhich can be injected inside the balloon through a second pipe from the surface (can this pipepass through the flexible pipe?). It also may be possible, in case such a formation is unavoidableto pump hydrates to the surface along the oil allowing from time to time some water to bepumped as wellThere may be other problems which are not known to me and which can be solved or theycannot. If I am informed for such problems I may have or may have not something to say on it.Offshore Energy Systems SA, 48 Karaoli & Dimitriou str. 15232 Halandri/Athens GreeceTel.: +302106775003, Fax: +302106812770, e-mail: daskalakis@martech.gr Page 7
  8. 8. Table 1. Simple calculations on the concept based on imaginary data Assumed input information z= 5000 m reservoir depth Pr 600 bar reservoir pressure Pr = 60000000 N/m2 reservoir pressure in Pascal h= 1500 m water depth Pw 15082875 N/m2 water pressure at sea bottom in Pascal Pw= 150.83 bar water pressure ρp 880.00 kg/m3 petroleum density ρw 1025 kg/m3 water density Well calculations up2/2 = 1,992.19 Equation (1) up 63.12 m/sec speed of oil flow inside well dw 100 mm well internal diameter Aw 0.01 m2 well section Qp 0.50 m3/sec oil flow rate 1,784.73 m3/h oil flow rate Flexible pipe calculations pressure driving oil from the balloon to the sea ΔPn 15,082,875.0 N/m2 surface uc2/2 2,424.6 Equation (2) 69.6 m/s speed of oil flow inside flexible pipe rs 0.91 Ratio of speeds (well/flexible pipe) rd 0.95 Ratio of diameters (flexible pipe/well) Balloon r 15 m radius of a spherical balloon V= 14,137.2 m3 The volume of the balloon time to fill the balloon with oil with the time to fill 7.9 hours calculated flow rate Buoyancy of the balloon completely filled with dead weight 2,049,889.2 Kg oil Additional weight required for holding 2,049.9 Tones capacityOffshore Energy Systems SA, 48 Karaoli & Dimitriou str. 15232 Halandri/Athens GreeceTel.: +302106775003, Fax: +302106812770, e-mail: daskalakis@martech.gr Page 8
  9. 9. 4. Concluding remarksA proposal is made which may give a solution of how to trap the oil coming out of the oil head ofthe Deep horizon oil field in the Gulf of Mexico and how to pump it out to a storage facility.The proposal needs elaboration to prove its applicability compared to other proposed solutions.BP engineers who have available all necessary information can do it. The concept can also beeasily and quickly tested in a laboratory.One major aspect is the practicality of the concept. Can it be realized quickly and beimplemented in the difficult conditions of the field and in such big water depths?In my opinion this is possible or else I wouldn’t make the proposal. A balloon of the sizerequired, I believe it is possible to be constructed by companies which are dealing with thematter, or probably a consortium of companies in the field. So is the required net.For the flexible pipe and the associated floaters and all the necessary calculations there existexperienced companies in the field.A last remark is that the concept presented here could work with a rigid steel structure insteadof the balloon.Such a structure (dome) I have seen in the news which was attempted to be installed over thewell head. I have no information on that. But if it was used to seal the well then I imagine thehigh pressures developed would prevent it.However, if the structure is installed in a way similar to proposed here, it can possibly work, i.e.there must be a gap between the bottom of the structure and the sea bottom so as to preventto develop high pressures inside it. Also the height of the structure has to be large enough toavoid collision of the oil beam on the internal dome surface and of course the rate of pumpingoil from the dome to be equal with the rate of oil flow coming out from the well.In case that it is expected to have events like blasting or sudden changes of pressure someabsorbing capabilities should be incorporated like those described before in the case of theballoon (see sketch 3).I remain at the disposal of any interested party for further evaluation.Offshore Energy Systems SA, 48 Karaoli & Dimitriou str. 15232 Halandri/Athens GreeceTel.: +302106775003, Fax: +302106812770, e-mail: daskalakis@martech.gr Page 9
  10. 10. Sketch 3. A way to realize the proposed concept with a dome instead of a balloon.Offshore Energy Systems SA, 48 Karaoli & Dimitriou str. 15232 Halandri/Athens GreeceTel.: +302106775003, Fax: +302106812770, e-mail: daskalakis@martech.gr Page 10

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