Downhole fluid properties optical analysis probe having a removable optical tip

1. A downhole fluid properties optical analysis probe to analyze at least one property of a multiphase flow mixture flowing in a hydrocarbon well has an elongated cylindrical body shape and comprises:

an optical tip at one end of the elongated cylindrical body arranged to be in contact with the multiphase flow mixture;

an optical link adapted for a connection with an electronics module at another end of the elongated cylindrical body arranged to be separated from the multiphase flow mixture, said electronics module comprising a light source;

wherein the optical tip is coupled to the optical link through a removable and watertight coupling being welds free and O-ring seal free, the removable and watertight coupling comprising:

a first portion of a protective tube resistant to downhole conditions, said first portion enclosing the optical link and comprising at least one first ring bulge close to a coupling zone;

a second portion of the protective tube partially enclosing the optical tip such as to let a distal end of the optical tip in contact with the multiphase flow mixture, said second portion comprising at least one second ring bulge close to the coupling zone;

a coupling tube surrounding facing ends of the first portion and the second portion, said coupling tube being adjusted in size to fit in between said first and second ring bulges; and

a coupling and protecting sheath enclosing said first ring bulge, coupling tube and second ring bulge in a watertight manner, said sheath being configured so that during use, the effect of pressure of the multiphase flow mixture flowing in the hydrocarbon well tends to apply said sheath onto the first and second ring bulges and the coupling tube such as to additionally seal the protective tube against the optical tip and against the optical link.

2. The optical analysis probe of claim 1 , wherein the ring bulges are chosen among the group comprising a ring bulge having a flat top, a ring bulge having a peaked top and a ring bulge having a rounded top.

3. The optical analysis probe of claim 1 , wherein multiple consecutive first and second ring bulges are positioned consecutively around the coupling zone.

4. The optical analysis probe of claim 1 , wherein the coupling and protecting sheath is made of a heat-shrink material.

5. The optical analysis probe of claim 1 , wherein the optical tip is made of a sapphire rod being needle shaped and having an external diameter ranging from 0.3 mm to 1 mm, and the link is an optical fibers bundle.

6. The optical analysis probe of claim 5 , wherein an index gel layer is positioned at the coupling zone between the optical fibers bundle and the other end of the optical tip.

7. A downhole fluid properties measuring tool comprising at least one downhole fluid properties optical analysis probe in accordance with claim 1 .

8. A production logging tool comprising a central pressure-resistant rigid housing carrying external centralizers adapted for contact with a production pipe wall of a hydrocarbon well and at least one downhole fluid properties optical analysis probe in accordance with claim 1 secured on an inner face of the centralizers deploying arms such as to expose an optical tip to a multiphase fluid mixture flowing in the hydrocarbon well, an electronics module of the optical analysis probe being located into said housing, a protective tube extending from the electronics module to the optical tip through a pressure feedthrough into said housing.

9. An optical tip of a downhole fluid properties optical analysis probe installation method, said optical analysis probe comprising an optical tip partially mounted into a protective tube resistant to downhole conditions letting a distal end of the optical tip in contact with a multiphase flow mixture and coupled to an optical link mounted into the protective tube at the other end of the optical tip through a removable and watertight coupling being welds free and O-ring seal free, the protective tube comprising a first portion and a second portion, the first portion enclosing the optical link and comprising at least one first ring bulge close to a coupling zone, the second portion partially enclosing the optical tip and comprising at least one second ring bulge close to the coupling zone, wherein facing ends of the first portion and the second portion are surrounded by a coupling tube that is adjusted in size to fit in between said first and second ring bulges, and wherein a coupling and protecting sheath encloses said first ring bulge, said coupling tube and said second ring bulge, said sheath being configured so that during use, the effect of pressure of the multiphase flow mixture flowing in the hydrocarbon well tends to apply said sheath onto the first and second ring bulges and the coupling tube such as to additionally seal the protective tube against the optical tip and against the optical link, the installation method comprising:

plugging facing ends of the first portion and the second portion into the coupling tube, and coupling together the optical link and the optical tip;

sliding the coupling and protecting sheath from the optical tip towards the coupling zone so as to cover said first ring bulge, said coupling tube and said second ring bulge; and

heating around the coupling and protecting sheath at least up to a temperature that causes shrinking of a heat shrink/retractable material forming the coupling and protecting sheath such as to generate a sealing.

10. An optical tip of a downhole fluid properties optical analysis probe replacement method, said optical analysis probe comprising an optical tip partially mounted into a protective tube resistant to downhole conditions letting a distal end of the optical tip in contact with a multiphase flow mixture and coupled to an optical link mounted into the protective tube at the other end of the optical tip through a removable and watertight coupling being welds free and O-ring seal free, the protective tube comprising a first portion and a second portion, the first portion enclosing the optical link and comprising at least one first ring bulge close to a coupling zone, the second portion partially enclosing the optical tip and comprising at least one second ring bulge close to the coupling zone, wherein facing ends of the first portion and the second portion are surrounded by a coupling tube that is adjusted in size to fit in between said first and second ring bulges, and wherein a coupling and protecting sheath encloses said first ring bulge, said coupling tube and said second ring bulge, said sheath being configured so that during use, the effect of pressure of the multiphase flow mixture flowing in the hydrocarbon well tends to apply said sheath onto the first and second ring bulges and the coupling tube such as to additionally seal the protective tube against the optical tip and against the optical link, the replacement method comprising:

cutting and discarding the coupling and protecting sheath;

disconnecting and discarding the optical tip from the optical link;

plugging facing ends of the first portion and the second portion into the coupling tube, and coupling together the optical link and a replacement optical tip;

sliding a replacement coupling and protecting sheath from the replacement optical tip towards the coupling zone so as to cover said first ring bulge, said coupling tube and said second ring bulge; and

heating around the replacement coupling and protecting sheath at least up to a temperature that causes shrinking of a heat shrink/retractable material forming the replacement coupling and protecting sheath such as to generate a sealing.