DEVELOPMENT OF A DRILL-CUTTING TREATMENT TO REDUCE HYDROCARBON CONTENT IN WASTE

DEVELOPING A NON-CONVENTIONAL, COST-EFFECTIVE AND AN ENVIRONMENT-FRIENDLY METHOD OF DRILL-CUTTING TREATMENT THAT CAN REDUCE HYDROCARBON CONTENT IN THE WASTE TO AN ACCEPTABLE STANDARD

This research was aimed at developing a non-conventional, cost-effective and environment-friendly method of drill-cutting treatment that can reduce hydrocarbon content in the waste to an acceptable standard within a short time.

GET RELATED RESEARCH MATERIALS HERE

CHAPTER ONE

INTRODUCTION

• BACKGROUND TO THE STUDY

Since 1956 when oil was discovered at Oloibiri (Onuoha, 2008; Anifowose, 2008),  exploration and production of oil have continued to date in the Niger Delta (Kadafa, 2012).

The drilling processes are usually conducted with drilling fluids (or muds) usually defined as “any of a number of liquid and gaseous fluids and mixtures of fluids and solids (as solid suspensions, mixtures and emulsions of liquids, gases, and solids) used in operations to drill boreholes into the earth” (Schlumberger, 2017).

Efforts to classify these drilling fluids often have produced more confusion than insight (Schlumberger, 2017). Meanwhile, two generic types are in existence i.e., Water-Based Fluids (WBFs) and Non-Aqueous Drilling Fluids (NADFs) (Agha and Irrechukwu, 2002; OGP, 2003). The NADFs or Oil Based Muds (OBM) are further classified into Low Toxic Mineral Oil and Synthetic or Pseudo Oil Based Muds (SBM or POBM) (Chaineau et al., 2003; Joel, 2013). Alternatively, using mud composition as the classification basis by distinguishing the component that clearly decides the performance and function of the fluid, classification of drilling fluids have also been done into: (1) gaseous (pneumatic), (2) water-base, and (3) non-water-base, some considerable overlap though may be observed in a number of their subcategories (Schlumberger, 2017).

Drill-cutting are brought forth as by-products of every drilling activity (Aird, 2008) and are composed of rocks, particulates and liquids brought to the surface in the course of drilling from geologic formations (Opete et al., 2010). Simply put, drill-cuttings are drilled rock components pieces that are returned to the surface with the drilling fluids (Agha and Irrechukwu, 2001).  While drill-cuttings from WBMs pose little environmental threat, especially in the deep offshore (Tilstone et al., 2012), those from OBMs have received worldwide prohibition (Wait and Sharma, 2009) even in Nigeria (DPR, 2002) sequel to their damaging environment impact (Chaineau et al., 2000, Perry and Griffin, 2001).

For example, improper drill-cuttings disposal impacts the soil, groundwater, vegetation, public and aquatic health (UNEP, 2011). This is because some hydrocarbons, most importantly, the PAHs (Polycyclic Aromatic Hydrocarbons) and the BTEX (Benzene, Toluene, Ethylbenzene and Xylenes) have shown negative environmental impacts and are consequently selectively treated in assessment and clean-up of oil spills (UNEP, 2011).

This is the reason for our nation’s NADF zero discharge requirement in onshore and swamp (including near offshore) locations (Agha and Irrechukwu 2001). These challenges notwithstanding, NADFs still enjoy patronage since they increase the Rate of Penetration (ROP) and reduce Non-Productive Time (NPT), thus saving overall development costs (Getliff et al., 2012).

Methods of managing drill-cutting are generally classified into three: thermal, physico-chemical (evaporation, leaching, and adsorption) and biological treatments (Chaineau et al., 2000). In Nigeria, currently, the Department of Petroleum Resources (DPR) has approved reinjection (CRI), thermal desorption (TDU) and dumping offshore with a proviso as methods of handling drill-cuttings (Agha and Irrechukwu, 2002). These methods unfortunately present with serious disadvantages. For instance, both CRI and TDUs treatments will demand large drilling waste volumes as well as the high initial capital outlay for effective implementation. Besides, both CRI and TDUs employ imported technology, besides, after treatment, the residue is observed to contain enormous level of pollutants (Veil and Dusseault, 2003; ESRF, 2004). Offshore Disposal is also reported to biologically affects marine life significantly (Wills, 2000).

Common examples of soil remediation techniques for petroleum hydrocarbons are evaporation, burying mechanically, dispersion and washing. Unfortunately, their effectiveness is in doubt as they consume time and money (Singh et al., 2012). Bioremediation or biological degradation enhancement, (Ibrahim, 2009) because of its environmental management and cost-effectiveness capabilities is obviously a promising technology for drill-cuttings handling (Das and Chandran, 2011). Bioremediation is also represented as the employment of microbes (bacteria and fungi) metabolic processes (biodegradation, bioaccumulation, biofermentation, bioabsorption, bioadsorption, etc) to degrade pollutants from the environment (Odokuma, 2012).

This study therefore sought to look into a non-conventional, cost-effective and environment-friendly biochemical remediation path which employs microorganisms together with chemical enhancers to reduce drill-cutting biologically into nontoxic residues.

• STATEMENT OF THE PROBLEM

UNEP Reported that water from 28 wells in 10 communities, in proximity to contaminated sites in Ogoniland was laden with hydrocarbon. They further stated that for instance, water from seven wells were 1,000 times more than the 3 μg/l, Nigerian drinking water standard.  The communities, though fully cognisant of such pollution and its attendant dangers, continue to utilise the polluted water for bathing, cooking, washing and drinking because of no alternatives. Similarly, UNEP reported that two-thirds of the polluted land sites in proximity with oil facilities, after detail assessment by her team, showed soil contaminations in excess of the Environmental Guidelines and Standards for the Petroleum Industry in Nigeria (EGASPIN) standards.  At 41 sites, pollution of groundwater by hydrocarbon had also exceeded the EGASPIN legislation standards (UNEP, 2011).

Furthermore, open dumping of some 1,000 – 1,500 m³ of drill-cuttings in hundreds of industrial packing bags were reported by the UNEP project team at a site formerly used for sand mine in Oken Oyaa in Eleme LGA. UNEP observed that such open dumping of hazardous waste in an unlined pit shows lack of custody chain between waste generators, transporter and disposal facility in the Niger Delta (UNEP, 2011).  This demonstrates how serious the issue of environmental degradation is in the Niger Delta.

Meanwhile, all the three approved methods for drill-cuttings handling in Nigeria, namely CRI, TDUs and disposal in the Offshore (EGASPIN, 2012), present with serious challenges. For example, both CRI and TDUs treatments will require large volume of wastes an enormous capital outlay for good implementation. Besides, both CRI and TDUs employ imported technology, and after treatment, the residues are reported to contain enormous level of pollutants (Veil and Dusseault, 2003; ESRF, 2004). Also, disposal of wastes offshore affects marine life (Wills, 2000; Allen, et al., 2007).

Bioremediation, owing to its low greenhouse gas, cost-effectiveness and low environmental footprints (Das and Chandran, 2011) has been recommended for the handling of drill-cutting in the region of Niger Delta (Zabbey et al., 2017).

However, previous attempts had not yielded expected success as a result of wrong operational assumptions (for example, conclusions by industry operators that a clay layer covers Niger Delta soil, hence percolation of oil will be retained in the topsoil, therefore making Remediation by Enhanced Natural Attenuation (RENA) desirable for the Niger Delta) and the employment of ineffective and incompatible processes (i.e. RENA) for such dynamic and complex environments (Zabbey et al., 2017).

Even though no particular bioremediation method was recommended by UNEP, most of the other microbial treatment methods require longer treatment periods, hence the necessity for a non-conventional, environment-friendly and cost-effective treatment option, which formed this study’s goal.

• AIM AND OBJECTIVES OF THE STUDY

This research was aimed at developing a non-conventional, cost-effective and environment-friendly method of drill-cutting treatment that can reduce hydrocarbon content in the waste to an acceptable standard within a short time.

The objectives of this study were as follows:

1. To evaluate the potential of natural soil bacteria to degrade the HC component of drill-cuttinG
2. To determine biodegradation rates
3. To determine the effect of treatment parameters on biodegradation rates.
4. To compare the effectiveness of biotreatment with other methods or processes.
5. To model the effect of the biochemical treatment parameters on biodegradation

• SIGNIFICANCE OF THE STUDY

UNEP findings has shown that, for instance, Remediation by Enhanced Natural Attenuation (RENA) (the only remediation method observed by UNEP in Ogoniland) has not been effective in Niger Delta because it is assumed that hydrocarbons will not go deeper, because of temperature, nature of the oil and an underlying layer of clay (UNEP, 2011). It is, therefore, necessary to work on a more environmentally friendly, cost-effective and locally available method for the Niger Delta. This will restore, among others, the land to its original condition and win the confidence of local communities, thus reducing litigations between operators and host communities.

Besides, the model equation developed on the biodegradation rate will help to reduce drill-cuttings’ treatment time since operators will be assisted to make informed decisions on treatment parameters’ optimization.

Furthermore, this study has generated much data for easy reference by oil industry operators and other stakeholders in environmental management profession.

• SCOPE OF THE STUDY

This study centered on developing a means of handling drill-cutting that are more effective, time saving and environment-friendly.

It involved conducting different microbial treatment protocols using, soil, dispersants, and nutrients separately and in combinations, on samples of drill-cuttings while monitoring their oil contents to ascertain the effects of parameters on bioremediation which was modeled thereafter.