Drilling of Horizontal Wells for Shale Gas Production fluids compatible with geological formations crossed • The correct choice of the drilling fluid is ... Under Balanced Drilling

Drilling of Horizontal Wells for Shale Gas Production

Ph.D. Professor. Avram Lazar

Oil & Gas University of Ploiesti

Main Themes 1. General aspects 2. Drill string composition 3. Drilling fluids compatible with geological formations crossed 4. Drilling methods optimization 5. Bottom-hole orientation 6. Case Study 7. Conclusions and proposals

General Aspects Main drilling types used for the exploitation of shale gas: - vertical drillings - drillings with large deviations:

Extended Reach Wells (ERW) Extended Reach Drilling (ERD)

In our country, horizontal wells have been drilled since 1995 starting with no.1 Clejani well. Directed and horizontal wells have been executed especially by S.C. Drilling Wells Tg. Mures. Thus, only in the period 2008 - 2012, this company has made a number of 34 such wells.

General Aspects

Chart of shale gas extraction

General Aspects

Construction program of a

bore hole ERW realized in Romania

Drill string composition

New technical proposals:

- increasing the length for internal upset joint;

- high-strength metallurgy application; - double shouldered connection; - using the new connections (non

standard); - using the new materials: titan;

aluminium; composite materials; - using the C. S. drill pipes, a.s.o.

Reel Well Drilling Method

drill string consists of two concentric tubes;

fluid circulation to the bit is done through the annular space between the two tubes; return fluid with detritus is through the inner tube

Drilling fluids compatible with geological formations crossed

• The correct choice of the drilling fluid is

one of the most important factor in making a well. This aspect integrates the drilling and the completion process in the cycle interdependent: Environmental policy - Planning - Implementation and Operation - Control and Corrective Action - Analysis made at management level.

Premises for particles transport problem

in the annulus space the flowing must be turbulent; on recommend drilling fluids with low viscosity; alternating the submersible drilling system with the

rotary system (if possible); the top drive system is preferable to the hydraulic

rotary system; making some short washing trips; diminishing the barite sedimentation; ensuring the stability of the bore-hole wall a.s.o

Recommended fluids types

• Drilling fluids with fragile gel; • Non dispersive fluids; • Clogged opening fluid; • Inverse emulsions; • Oil-based fluids; • Clear fluids; • Synthetic fluids; • Biopolymers fluids; • Preformed foams e.s.o.

Preparation of bore holes interval

Main target: ensuring the column introduction to the projected depth.

Problems to be solved in preparing the highly

inclined intervals: kneeling (dog-leg-sized) and large portions with very big curves correction complete evacuation of detritus conditioning the drilling fluid for preventing instability occurrence and reducing the friction coefficient

Drilling methods optimization

Under Balanced Drilling (UBD); Managed Pressure Drilling (MPD); Closed Loop Drilling System; Reel Well Drilling Method

Closed Loop Drilling System

Bottom-hole orientation

Main problems: changing the well trajectory from vertical to

horizontal; keeping the well trajectory in the horizontal portion; detritus evacuation in the horizontal zone; drill string maneuver in the horizontal portion; achievement the WOB in the horizontal zone; avoiding the loss of stability for drill string, e.s.o.

Modern orientation technologies

Geosteering Method; Automation Technology for

Directional Drilling; Rotary Steerable System; Reel Well Drilling Common point: using the bottom-hole

engines and MWD systems

Case Study

Most favorable reservoir conditions regarding bituminous shale formation type and, at the same time, having an exploitable gas containment, are represented by Oligocene deposits of the Miocene-Pliocene area and by the Paleogene flysch from Romania. The Pucioasa layers with sandstone layers of Fusaru have the greatest depth: 500 – 1000 m (in the northwest sector, thickness can reach 1500 – 2000 m). There are three distinct levels:

the lower level that consists mainly of disodiliforme marl and, from place to place, sideritic limestone; the middle level consists of Fusaru calcareous sandstone type; the higher level, like the lower one, consisting of marls with intercalations of disodium.

Case Study

Most favorable reservoir conditions regarding bituminous shale formation type and, at the same time, having an exploitable gas containment, are represented by Oligocene deposits of the Miocene-Pliocene area and by the Paleogene flysch from Romania. Lithological succession of Kliwa ologiocene sandstone deposits, in marginal facies includes the following levels :

lower disodium shale Kliwa sandstone (lower level) layers of Podu Morii Kliwa sandstone (upper level) disodium and Menilite (upper).

Podul Morii layer has the maximum thickness (about 700 m), and it is composed of an

alternation of peliticrocks (brown clays, marls and sometimes volcanic tuffs) and sabulous rocks (sandstones and sands).

Case Study

Oligocene deposits sequence

a) Pucioasa-Fusaru b)-Kliwasandstone c)-under Carpathian area

Case Study

The most favorable conditions for the exploitation of shale gas are present in Pucioasa-Fusaru litofacies layers. These litofacies layers can be distinguished by an important classification and sedimentation rate. They are composed of pelagic and semi-pelagic clays, mostly bituminous, alternating with fine or sandy gritstone. At the top of Pucioasa-Fusaru litofacies, due to the growing content of calcium carbonate, clays are replaced by marls.

Case Study

Calculating the characteristic points of the horizontal wells profiles: the vertical depth of the well H = 2000 m; casing shoe of anchorage column depth h1 = 500 m; the depth where is localized the initiation of diversion point (from the casing shoe of the anchorage column) h2 = 1000 m; horizontal section length a3 = 500 m; intensity of vertical deflection iv = 1°/ 10 m; the radius of curvature: R = 573 m the acceptance angle

Case Study

180R

180R

Points characteristic values estimation

Case Study

180R

180R

Profile of the proposed well

Conclusions and proposals

1. Currently, for the exploitation of shale gas, horizontal drillings are used most efficiently, most often, combined with hydraulic fracturing operation. It is especially the case of the extended-action drilling ERD (Extended Reach Drilling) with lengths of horizontal portions of thousands of meters. At present, there are established several modern guidance technology that can fit these issues: the method of crew drilling (geosteering), Automation Technology for Directional Drilling, Rotary Steerable System, Reel Well Drilling – that use bottom engines and measurement devices while drilling (MWD). In our country, horizontal wells have been drilled since 1995 starting with no.1 Clejani well. Directed and horizontal wells have been executed especially by S.C. Drilling Wells Tg. Mures. Thus, only in the period 2008 - 2012, this company has made a number of 34 such wells.

Conclusions and proposals

2. The correct choice of the drilling fluid is one of the most important factor in making a well. This aspect integrates the drilling and the completion process in the cycle interdependent: Environmental policy - Planning - Implementation and Operation - Control and Corrective Action - Analysis made at management level. 3. Application and improvement (if possible!) of the modern drilling methods (Under Balanced Drilling - UBD, Managed Pressure Drilling – MPD, Closed Loop Drilling System and Reel Well Drilling Method it is absolutely necessary!

Conclusions and proposals

4. We propose below, a five-stages scheme for the exploitation of a shale gas reservoir (the first two we can find almost done): The first phase, lasting from 1 to 3 years, is to identify the shale gas

resources; The second phase, lasting from 1 to 3 years, is a preliminary

assessment that includes evaluation of surface expansion of the shale gas accumulation;

The third step is the pilot drilling project; The fourth stage corresponds to the production pilot testing; The fifth stage, and the last, is represented by the commercial

exploitation.

Thank you!