Utilizing Nanotechnology to Solve Drilling Problems in Iraqi Oil Fields

Nanotechnology is a recent technology which is used in all industry sectors. In the oil and gas industry, this technology is commonly used due to its importance in solving the problems encountered while drilling operations and production stages. Nanotechnology can be used to improve the drilling process by adding nano-materials to drilling fluids in order to reduce drilling problems. This research is extended to previous research that published in journal of petroleum research and studies to compared the effect of nano-materials [Commercial nano-materials Multi Walled Carbone Nano Tube (MWCNT) and nano silicon oxide (SiO2) with nano-silica (rice husks, that prepared in PRDC labs) on water base drilling mud properties]. All characterization tests were achieved by the Nanotechnology and advanced materials researches center it is belongs to the University of Technology. The investigated properties of drilling mud included rheological properties and filtration. All tests are conducted according to API specifications (American Petroleum Institute). The results show an improvement in the rheological properties (plastic viscosity, yield point, apparent viscosity and gel strength) and filtration after adding the commercial MWCNT, nano silicon dioxide(Sio2) and the prepared nano-silica (rice husks) to the water based mud. The results of plastic viscosity of MWCNT,Sio2 and nano silica(rice husks) are 12,20,8 cp after adding 0.7 gm to the water base mud while the amount of filter is 11.8 ml after adding nano particle size of MWCNT , nanoSio2 and 11.6 after adding nano silica(rice husks). The prepared nano silica (rice husks) gave results similar to the results of the commercial nano silicon dioxide (SiO2). Therefore, using of nano silica (rice husks) can be cost effective due to producing these materials locally instead of using the commercial nano SiO2.


Drilling Fluids
Drilling fluid a heavy and viscous fluid mixture that is used in drilling operations to carry rock cuttings to the surface, controlling pressure, stabilizing exposed rock, providing buoyancy and to lubricate and cool the drill bit.

Effects of Nano Particles on Drilling Fluids
Nano-fluids can be designed by adding nano-sized particles in low volumetric fractions to a fluid. The nano-particles can be improving the rheological properties, thermal and mechanical properties [2] .There is some applications of nanotechnology in drilling fluids:

Rheological Properties
Rheology is a part of science of deformation and matter flow. Using nanoparticles to improve the performance of drilling fluids is a recent development [3].

Wellbore Stability and Fluid Loss Control
The filter cake developed during the nano-particles based drilling fluid filtration is very thin, for reducing formation damage and differential pressure sticking problem while drilling operation. Nano-particles can be added to the drilling fluid to minimize shale permeability through plugging the nanometer-sized pores and shut off water loss [2]. fluids by forming a continuous thin films to lubricate at the wall/pipe interface.
Nanoparticle-based fluids could be useful in reducing the torque and drag problems in horizontal, multilateral, and coiled-tubing drilling.

The Aim of the study
The aim of this study is to examine the effect of nano-material by adding it to water based drilling mud and the performance of this nanomaterial on the filter loss and rheological properties of water based drilling mud.

Theoretical Background
The drilling fluid is related either directly or indirectly to almost every drilling problem. Selection and application of the drilling fluid are key factors in success of drilling operation. All drilling fluids can have a wide range of chemical and physical properties. These properties are specifically designed for drilling conditions and the special problems that must be handled in drilling a well [4].

Nano-Materials
Good formulations of drilling fluid properties are required in the drilling operations.
Choosing of suitable drilling fluid additives are important in performing of drilling fluid. The nano-materials are selected due to its extremely high surface area to volume ratio and high thermal conductivity. This research focuses on use of nanosilicon materials, nano silica (rice husks) and the multi-walled carbon nanotubes (MWCNT) to investigate the effect of these nano-additives on filter loss and rheological properties of water based drilling mud.Nano-materials are considered the most promising material for smart fluid design due to different and highly enhanced physio-chemical, electrical, mechanical, thermal, properties and interaction potential of nano-materials compared to other materials. Physically, particle size of nano has a dimension that is thousand millionths of a meter. Hundred nanometer fibers or particles have diameters that are about 800 to 1000 times smaller than the diameter of a human hair [5].Based on the number of particle size additives in the fluid, these fluids can be classified as simple and advanced nano-fluids. Nano-fluids with one nano of sized additive are defined as simple nano-fluids; nano-fluids with more than one nano-sized additive are clssified as advanced nano-fluids. A nano-material could be single or multifunctional. A multifunctional nano-additive can perform several jobs in the fluids systems to complete the functional tasks of the fluid with a reduction in total solids and/or chemical content of a mud and also the overall fluid cost. The natures of a nanomaterial have a very high specific surface area with enormous area interactions just require very low concentration of a nano-material to provide good enhancement in fluid properties [6].
The following nano-materials were used in this research:

Multi-walled nanotube (MWNT)
MWNT consist of multiple rolled layers of grapheme [7].There are two models to describe the structures of MWNT. Russian Doll model, sheets of graphite are arranged in concentric cylinders and Parchment model, a single sheet of graphite is rolled in around itself.

NanoSilicon
Silicon dioxide nano-particles are the basis for a great deal of biomedical research due to their low toxicity, stability and ability to be functionalized with a range of molecules and polymers. Nano-silicon properties can be categorized as follows:  [8].In this research, two types of nano-silica were used as follows: 2. Nano Silica (Rice).

Apparatus and Experimental Work
many tests carried out in laboratory to investigate the effect of adding nano-materials on the rheological properties and filter loss of drilling fluids.

The Laboratory Apparatus
Many of apparatus are used such as Viscometer (model 800), mud balance, low pressure filter loss and pH meter.

Materials
A brief description of additives and chemicals that used in our research is listed below:

Bentonite
It is considered the most widely additive that use in the drilling fluids. Bentonite is consisting from fine-grained clays that contain not less than 85% Montmorillonite.
Bentonite is classified as sodium or calcium bentonite, depending on the exchangeable cation. In fresh water, sodium bentonite is more reactive than calcium bentonite [10].

Caustic Soda or Sodium Hydroxide (NaOH)
It is used to raise pH in water based drilling fluid, to solubilize Lignite, Lignosulfonate and tannin materials, to neutralize Hydrogen Sulfide and to counteract corrosion

MWCNTs
It is used to enhance of rheological properties in water-based drilling fluid. This material is commercial and its specification satisfies the nano-material properties

Silicon Dioxide (SiO2)
It is a powder that used to improve the rheological properties and filter loss with OD >40nm. SiO2is commercial and its specification satisfy nano-material properties.

Chemical Preparation of Nano-silica (rice husks)
The procedure of preparing the nano-silica (rice husks) as follows: 1-The rice husk soaked in distilled water overnight and washed thoroughly with distilled water to dry overnight in an oven at 90°C.    All characterization tests were achieved by the Nanotechnology and advanced materials researches centre which belongs to the University of Technology.

3.2.6.2b Results of Scanner Electronic Microscope (SEM)
SEM test has been achieved to determine the surface type, form and size of the prepared material. respectively. From these figures, it can be noticed that silica SiO 2 as spherical nanoparticles with a diameter 100-150 nm. The form and the composition of the nanomaterial depend on the preparation method, type and purity of the chemical materials.

Adding MWCNT the Water Based Mud
After the preparation of the samples and aging for 16 hrs for hydration, the measurements of viscosity, mud weight, pH and filter loss at laboratory condition for different concentrations. The results were taken as shown in Table (1).

Effect of Adding Nano Silcon Dioxide (Sio 2 ) to the Water Based Mud
The results of adding the nano SiO 2 are shown in Table (2).

Adding Nano Slilica (Rice Husks) to the Water Based Mud
After the preparation of the samples and aging for 16 hrs for hydration, the measurements of viscosity, mud weight, pH and filtration at laboratory condition for different concentrations. The results of adding nano-silica (rice husks) was depending as shown in Table (3).  The apparent and plastic viscosity of water based mud with MWCNT was higher than The results indicates that the nano-silica (rice husks prepared in PRDC labs) and the commercial nano-silica SiO 2 similar results to improve the mud properties. Therefore, a comparison was made between those two materials.
The comparison of apparent viscosity (AV) of the conventional mud and nano-silica (rice husks) with water-based mud and nano-silcon dioxide (SiO 2 ) were investigated and shown in Figure (6).The apparent viscosity (AV) of nano-silica (rice husks) and nano SiO 2 were slightly higher by increasing the concentration of nano-silica (rice husks) and the commercial nano SiO 2 than that of the conventional water-based fluids. PV of water based mud with nano-silcon dioxide (SiO 2 ) was slightly higher than water based mud with nano-silica (rice husks) as shown in Figure (7). The yield point (YP) of water based mud with nano-silica (rice husks) was slightly higher than water based mud with nano-silcon dioxide (SiO 2 ) as shown in figure (8).