Karachaganak: Path to Success
More than fifteen years ago, primary goal of Karachaganak Petroleum Operating b.v. (KPO) was to increase production to a completely new level. Together partners have applied industry leading hydrocarbon technology to one of the world’s most complex reservoirs.
As a result, the infrastructure was modernised and a whole range of new production facilities were built, including hydrocarbon processing plants, a 160 MW power station, and more recently, the Karachaganak – Uralsk gas pipeline. For the first time in Kazakhstan, technically complex wells were drilled at Karachaganak, including multi-lateral wells. An innovative sour gas re-injection project was implemented successfully. This state-of-the-art technology has proven to be very effective, since it makes it possible to boost the production of hydrocarbons while caring for the environment. This technology has generated significant value for the Republic of Kazakhstan.
Drilling performance on the field has improved significantly over the last 5-6 years, from drilling a standard sub-horizontal new well within 6 months to the current stage where a similar well is drilled in circa 90days (3 months).
Drilling in the overburden usually took close to 3 months to complete, with the remaining time used to drill in the reservoir with 8 ½” hole building angle to sub-horizontal and finishing the well in 5 7/8” or 6” hole. Currently the overburden is drilled within 1.5 months and the reservoir zones in similar time. The challenge therefore has been to optimise drilling through the reservoir, especially through the build section in order to improve on overall drilling performance.
This entails reducing the number of drilling trips to complete the build section, which normally takes several BHA trips, starting with a Positive Displacement Motor or PDM assembly. Previous attempts to drilling the 8 ½” build section in one go with Rotary Steerable Systems (RSS - both Point-the-Bit and Push-the-Bit systems) from different Service Providers have been unsuccessful. Likewise, apart from drilling the 8 ½” build sections in new wells with several PDM assemblies, attempts to drill 6” build sections in deepening sidetracks with Rotary Steerable Systems (RSS) have also failed in the recent past.
Today at Karachaganak, an innovative Hybrid RSS system, combining the Point-the-Bit and Push-the-Bit technologies (PowerDrive Archer 475 from Schlumberger) has been introduced on a re-entry sidetrack in 6” hole from existing wellbore.
The PowerDrive Archer 475 Rotary Steerable System has the capability to drill hole sizes from 5 7/8 to 6 ¾” and delivers up to 18°/100 ft doglegs in rotary mode. This exciting new addition to the family of RSS is extremely versatile, delivering both high DLS wells and low DLS wells in difficult formations where conventional RSS struggle. PowerDrive Archer RSS (PDA) is able to deliver well profiles previously only possible with Positive Displacement Motor down hole (PDM) with an improved wellbore quality and rate of penetration (ROP) of a standard rotary steerable system(RSS). The unique hybrid action makes it a superb choice for directional open-hole and whipstock sidetracks, even at low inclinations. This allowed the KPO WEOPs team to drill this re-entry well in one BHA run. Several planned trips were avoided resulting in significant time savings.
A specially designed polycrystalline diamond (PDC) bit with tapered gauge was used to ensure the best building capacity to the BHA and to reduce vibrations.
The 4.75” Nominal OD PowerDrive Archer tool was selected to drill the well 9813 side track (6” hole section) in order to achieve the following goals:
- Drill both the build-up section and the tangent section in one run in the reservoir (total 1362m with 6° DLS) saving time and reducing the costs.
- Guarantee smoother bore hole quality in the build- up (BU) section when compared to the one drilled with a PDM and this in turn will facilitate running the down hole lower completion tools
- Increase the reservoir exposure of the well
Some of the benefits and rational for selection of Power Drive Archer 475 as a means to improve on drilling performance in the build sections included:
- Potential time saving compared to PDM in drilling BU sections (no time spent in orienting the bit and longer lasting)
- Higher DLS capability leading to deeper KOP and increased reservoir exposure compared with standard RSS.
- Improved hole quality in the BU section facilitating the run of casings/tubings and reducing risks
- Ability to drill sub-horizontal build sections and deepening sidetracks in one run.