**3.1 Drilling for 8½″hole section with steel drill pipe**

The root causes for different problems encountered on the 8½ section in well drilled in Algeria are;


#### **3.2 Load summary**

According to **Table 3**, the drill pipe is exposed to fatigue failure during all operations, which is naturally related to the well trajectory, which has some


*- Tripping in: when running in hole (RIH)*

*- Tripping out: when pull out hole (POOH)*

*- Rotating on bottom: means that the pipe rotates with axial movement.*

*- Rotating off bottom: means that the pipe rotates without any axial movement*

*- Backreaming: the practice of pumping and rotating the drill string while simultaneously pulling out of the hole.*

#### **Table 3.**

*Load summary for steel drill pipe.*

tortuosity as shown in **Table 4**, which displays doglegs per unit length in the string during drilling operations and located points along the well that may be subjected to high severe doglegs leading to a high degree of severity of the moment bending on the mentioned areas. For that reason; the solution proposed in this paper consists in simply replacing joints of standard steel drill pipe with lighter aluminum drill pipe while keeping the same bottom hole assembly (BHA).

Thus; A torque and drag optimization study has been run to determine the optimum number of ADP joints along the drill string to minimize friction and reduce compression along the well trajectory and limit the maximum depth which can aluminum drill pipe reached without any failure, accordingly, 150 joints of standard steel DP have been replaced by aluminum DP above the BHA. **Table 5** represented below give the main characteristics of ADP.

#### **3.3 Results and interpretation**

The results exposed in **Table 6** indicate that aluminum drill pipe gives good results in tortuous intervals compared to steel drill pipe but in total depth do not exceed the 4000 m.

This result is confirmed by the output obtained in the torque drag effective tension graph which has included the graphical curves on tension vs. distance along with string (tension limit, helical buckling, sinusoidal buckling, in all operations (rotate off bottom, rotate on bottom, tripping out, tripping in).

Accordingly; it is obviously seen that all operations curves do not cross the Tension Limit curve; the drill string is located into a safe window; therefore, there is no danger of exertion the aluminum drill pipe in the tortuous interval, as depicted in **Figure 1**.

Thus we can assume that the 0.2032 m drilling phase benefited from ADP for the reason that; First of all aluminum drill pipe has significantly good fatigue, which is confirmed by the fatigue ratio value which is 0.642 less than 1. As shown on **Figure 2**.

Fatigue ratio Rf <sup>¼</sup> <sup>σ</sup>bending þ σbuckling σfatigue Limt ¼ 1 is equal to the safety limit (1)

where σbendiing ¼ σflexion [6].


### *Mechanical Resistance of a Superficially Treated Alloy Drill Pipe during Onshore Drilling DOI: http://dx.doi.org/10.5772/intechopen.101867*

**Table 4.**

*Variation in wall trajectory via tortuosity.*

### *Mechanical Resistance of a Superficially Treated Alloy Drill Pipe during Onshore Drilling DOI: http://dx.doi.org/10.5772/intechopen.101867*


### **Table 5.**

*Details in each specific drilling string and section.*


*- Tripping in: when running in hole (RIH)*

*-Tripping out: when pull out hole (POOH)*

*- Rotating on bottom: means that the pipe rotates with axial movement.*

*-Rotating off bottom: means that the pipe rotates without any axial movement*

*- Backreaming: the practice of pumping and rotating the drill string while simultaneously pulling out of the hole.*

#### **Table 6.**

*Load summary for aluminum drill pipe.*

Secondly; the 0.2032 m drilling phase benefited from (aluminum drill pipe) ADP since there was a considerable reduction of the surface torque and hook load as illustrated in **Figure 3**, for the reason that there was a reduction in side force as represented in **Table 7**.

As a final point; analysis of stresses in drill pipe and their results on each one, are shown on the graph cited, in **Figure 4** which gives us the different results for the Stresses (psi), the critically of Failure will depend on the value of these stresses. The Von Mises yield condition, states initial yield limit is based on the combination of the three principal stresses axial stress, radial stress, and hoop stress [3].

$$
\sigma\_{\rm VM} = \sqrt{\frac{\left(\sigma\_r - \sigma\_h^2\right) + \left(\sigma\_d - \sigma\_r\right)^2 + \left(\sigma\_h - \sigma\_d\right)^2 + 6\sigma\_s^2 + 6\sigma\_t^2}{2}} \tag{2}
$$

*σVM*: Von misses stresses, *σa*: axial stress, *σr*: radial stress, *σh*: hoop stress, *σt*: torsion stress *σS*: shear stress [6].
