Syria 2007

Problem:

A well in eastern Syria was drilled underbalanced through the Shiranish formation, which is a highly permeable low volume hydrocarbon bearing formation. Hydrocarbons were depleted from the formation and the well drilled ahead to 3338 m MD. At this depth it was necessary to change bit. While running back in the hole controlled gains were taken. When approaching the bottom the hole became thigh, which required washing and reaming, and, subsequently, the drillstring parted at the kelly saver sub and dropped 28m. An unsuccessful attempt was made to fish the string, although no proper overshot was found in the country. An influx of 60 bbls was taken and the shear rams were closed. An attempt was made to reduce pressure by lubricating mud, but this proved difficult as the annulus was narrow and the mud very viscous. The shut-in pressure finally stabilized at 3000 psig

Remedial Strategy:

Several options were identified for forward intervention, including: 1) Continue with volumetric lubrication using heavy mud (slow progress, difficult to get mud to swap with hydrocarbons), 2) Bullheading heavy mud (could break the 7" shoe and worse case broach to surface), 3) Stripping in coiled tubing circulating into drill string (success depended on drill string/annulus communication), 4) Relief well intersection (limited risk, high probability of success). Based on a detailed assessment of these options, it was decided to drill a relief well that would intersect above the Shiranish formation, which was predicted to be the flowing formation. The hydrocarbons would then be displaced using a modified drillers method, equivalent to having the bit off-bottom and mud circulated down the relief well and out the choke manifold of the target well.

Special Services:

John Wright Company, Alert Disaster Control, Wellflow Dynamics and Vector Magnetics was mobilized to assist in the recovery operation. JWCO supervised the special services required for the relief well intervention project. This included on-site supervision of directional drilling, surveying, kill operations and casing detection. Alert Disaster Control acted as the general contractor. Well Flow Dynamics was instrumental in the diagnostic investigation and in simulating various kill scenarios for possible kill operations using OLGA-WELL-KILL.

Challenges Met:  The project was complicated by the following:

  • As no gyros were available in the country and the MWD signals were highly corrupted by magnetic interference from the target well, the directional surveying had to be accomplished by electromagnetic ranging and magnetostatic interference analysis alone.
  • The well intervention was accomplished by a unique modified drillers method that had not been attempted before.
  • The choke operator and pump operator was located on a separate rigs, which made the communication path complicated. This challenge was overcome by using cell-phones.
  • As the target well contained a combination of oil, gas and several slugs of mud with different density, determining the pressure profile in the target well ahead of intersection was difficult.

 

Results:
  • The relief well located the target well at 2160m MD 21 5m away.
  • The combination of Wellspot electromagnetic ranging and passive magnetics analysis worked as planned and facilitated an efficient well intersection process.
  • The target well was successfully intersected at 2828m MD/2760m TVD.
  • The hydrocarbons in the target well was circulated out according to the modified drillers method kill plan, which was developed based on simulations using OLGA-WELL-KILL.