Rogers, Clint (Smith Bits a Schlumberger Company) | Jangani, Reza (Smith Bits a Schlumberger Company) | Spedale, Angelo (Smith Bits a Schlumberger Company) | Sadawarte, Sagar (Smith Bits a Schlumberger Company)
The Mereenie development project is targeting oil and evaluating natural gas reservoirs in the lightly drilled Amadeus Basin. In 2012, an operating company started searching for methods to improve rate of penetration (ROP) drilling the 8¾? vertical hole section through the difficult Stairway and Pacoota sandstone formations. The lithology consists of very abrasive and hard siltstone/sandstone with UCS up to over 30,000 psi. The hole section starts at 500 m and generally requires 700 m of total wellbore to reach KOP at 1200 m. The section has historically been drilled with PDC and Roller Cone bits with mud as the circulating medium. Both types of BHAs produced unacceptably slow ROP and required multiple trips to reach TD. The operator required a new approach.
To accomplish the objective, the operator wanted to switch from mud to underbalanced drilling using an air percussion BHA equipped with a hammer bit. However, an analysis using a well records database showed that only short (10–30m) shallow surface intervals had been drilled in Australia with percussion air hammers mostly in mining applications in the 1980–90's.
To increase the chance for early success, the operator wanted to import the latest air hammer tools and drilling techniques from North America. The provider suggested taking lessons learned from the Northeast USA where air hammer drilling plays a major role in developing oil and gas reserves in the region. The two applications are similar with regards to formation characteristics and the drilling team concluded the provider's downhole tool technology, service culture and experience/expertise would be integral to project success. In Q4 2013 the provider drilled the fastest and deepest percussion air hammer run in Australia's Oil and Gas history at 24 m/hr, 700% faster than the previous ROP achieved with PDC or Roller Cone.
EQT Production has implemented a new technique for drilling horizontal wells in the hard formations of the Appalachian Basin. Air percussion drilling has been adopted for use horizontally in the Berea sandstone, a hard and abrasive sandstone reservoir that had been traditionally drilled with roller cone bits. The evolution of the technology started with a packed-hole assembly that was trialed on three wells using stabilizer placement to provide directional control in the horizontal. The results were promising as penetration rates increased, but many trips were required to keep the wellbore in the desired target zone. To improve directional
control, a percussion BHA with a bent housing positive displacement motor (PDM) was implemented. The introduction of the positive displacement motor with the air hammer produced the same penetration rates seen in the packed-hole assembly while providing the directional control needed. Since mid 2009, the PDM percussion assembly has become the standard practice for drilling Berea horizontal wells, replacing the roller cone BHA. Through June 2010, over 40 wells have been drilled using the assembly. The lateral portion for a majority of the wells is now drilled in one run, reducing total drilling time from 22 to 13 days, dry hole costs by over one half and total well costs by about one third.