The sectional view of three different damaged regions (marked P, Q and R) near the vicinity of a perforation is shown in the figure above. Choose the correct option matching the entries in GROUP X with the corresponding terms in GROUP Y.
GROUP X P Q R
GROUP Y (I) Grain fracturing (II) Charge and core debris (III) Compacted pulverized zone
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Move outward from the tunnel tip: debris packed at the very tip, cracked individual grains right against the tunnel wall, and a wider crushed/compacted halo farther into the rock.
Step 1: Understand the geometry of the sectional figure: The figure shows a sectional (cutaway) view of a single perforation tunnel that has been shot through the casing, cement and into the formation, with the direction of perforation running left to right. The tunnel itself appears as the pale channel in the centre, and around it the diagram marks three distinct damaged regions with the labels P, Q and R, moving from the tip of the tunnel outward into the surrounding rock. Step 2: Identify region P, at the very tip of the tunnel: Label P points to the small dark region right at the forward tip of the perforation tunnel. This is where the shaped charge jet finally loses its energy and stops penetrating. Fragments of the charge case, the crushed liner material and broken rock (core) debris from the jet get packed into this tip region, often partially blocking it. This is the charge and core debris zone, GROUP Y statement (II). Step 3: Identify region Q, immediately around the tunnel wall: Label Q points to the hatched band that lies directly against the wall of the tunnel channel. This is the region where the very high transient stress of the perforating jet has fractured individual sand grains without fully crushing and compacting the rock fabric. This grain level cracking reduces the strength and alters the pore structure of the rock immediately bordering the tunnel, and it is described as grain fracturing, GROUP Y statement (I). Step 4: Identify region R, the outer shaded halo: Label R points to the wider grey shaded region that surrounds the tunnel and the grain fractured band. Here the rock grains have been pushed together and pulverized by the shock of perforation, filling the natural pore spaces with crushed fines and lowering the permeability of the formation over a wider halo around the perforation. This is the compacted pulverized zone, GROUP Y statement (III). Step 5: Combine the three matches: Putting the identifications together gives P - II, Q - I, R - III, which corresponds to option (D). Final Answer: \[ \boxed{P-II;\ Q-I;\ R-III\ \text{(Option D)}} \]
