Cuttings Re-Injection as an Environmentally Safe and Economically Efficient Drilling Waste Management Option for Karachaganak Field

Abstract

While engineered, operated and monitored properly, Cuttings Re-Injection or Waste Injection (WI) -injection of drilling generated waste into selected subsurface formations through initiation of disposal fractures -has proven to be an environmentally friendly and cost-effective waste management technology allowing compliance with "zero discharge" requirements. Areas where it is becoming the technology of choice are continuously expanding and the FSU (Former Soviet Union) is not an exception. The first WI project in this region started in Russia (offshore Sakhalin) in 2000 and then was followed by projects in Azerbaijan (ACG) in 2006 and mainland Russia (Western Siberia) in 2008 1,2,3 . To date, more than 4.5 MM barrels of waste have been safely injected in the region with extremely low NPT -0.01%. Karachaganak is a giant gas-condensate field in Kazakhstan operated by KPO. Re-injection of drilling generated waste into a selected subsurface formation has been under investigation as a potential waste management option for the field for a few years. Lithostratigraphy and geological characteristics of sub-surface formations were investigated to identify availability of suitable intervals for cuttings injection. Further, a feasibility study identified thick interbedded sandstone/claystones of the Triassic and Upper Permian, as suitable for WI purposes. Hydraulic fracture simulations showed containment of disposal fractures within the target injection intervals and indicated sufficient disposal capacity of selected formations. Once the potential disposal formations were identified, the basic surface equipment and facilities capable of safely handling expected drilling waste was designed. Additionally, as there was no actual precedence of WI technology implementation in Kazakhstan, local regulations were briefly reviewed. Summarizing, the given paper outlines results of feasibility investigation and required surface facility and equipment parameters for WI technology implementation in the Karachaganak field.

Deep Underground Injection of Waste from Drilling Activities—An Overview

“…Although the slurry waste is traditionally injected by a positive displacement plunger or piston/liner-type triplex mud pumps, new laboratory research and a field trial conducted by Newman et al [34] indicate that multistage centrifugal pumps could be advantageous in some situations. In some situations, as in the case of oil and gas exploration and production waste injection in polar regions, it is necessary to heat up the waste slurry preparation water because of frozen waste material in the reservoir pits [41] or to apply winterized measures for the entire unit to assure a minimal internal temperature of 17 °C [50,52].…”

“…In Figure 2, the waste slurry and disposal unit are shown in detail, as well as all options for adequate deep underground disposal [53]. In some situations, as in the case of oil and gas exploration and production waste injection in polar regions, it is necessary to heat up the waste slurry preparation water because of frozen waste material in the reservoir pits [41] or to apply winterized measures for the entire unit to assure a minimal internal temperature of 17 • C [50,52].…”