Large-diameter, long-interval tubing-conveyed perforation (TCP) operations are an important part of modern deepwater completion designs. Perforation jobs typically place a large dynamic load on the downhole equipment. Predicting the magnitude and transient behavior of such loads is a critical step in developing completion designs that avoid damage or destruction to tool strings and production equipment. Consequently, numerical modeling for accurate prediction of pre-job perforating designs is critical to mitigating risk for completing complex wells in a cost-effective manner.The paper presents numerical simulations that are conducted using a dynamic perforation modeling tool. The modeling software is an engineering and scientific tool that simulates the dynamic response of a cased or uncased wellbore, its contents, and the porous rock formation to the energy released by gas-generating and stored pressure sources. In particular, the model can be applied to predict the shock loads generated during TCP operations. This paper presents successful predictions of pressure transients for deepwater well completions in West Africa and the Philippines. The results from both examples demonstrate how simulations are used to mitigate risk and design successful completion strings. In addition, some recent improvements to the modeling platform are presented, including a more efficient pressure solver, the implementation of a new tool-string friction model, and a new interface to the simulation output data. Finally, the paper ends with the next steps in the development of shock modeling capabilities of the software.

This paper was prepared for presentation at the 1999 SPE Annual Technical Conference and Exhibition held in Houston, Texas, 3–6 October 1999.

Perforation operations are an important part of the well completion process in many field developments today. However, there are two considerations paramount to such a design. First, the post-job well production rate depends critically on a complex system in which the formation, perforations, and wellbore are dynamically and nonlinearly coupled together. Second, perforating operations can place a large dynamic load on downhole equipment. Predicting the spatial loading and its transient behavior is an important step in a completion design that implements risk mitigation to avoid damaging downhole equipment. In this study, we use a numerical modeling tool that has been used to simulate the dynamic behavior of the wellbore-reservoir system during perforating pre-job design. A typical case for this modeling software generates a quantitative prediction for the transient distribution of pressure, mass, velocity, and energy from the perforating event. These transients are commonly analyzed and incorporated into completion designs. In this paper, two critical components of modeling relative to perforating job design will be evaluated and characterized. First, the wellbore-perforation-formation coupling will be evaluated and characterized using a modified version of the code designed to model API RP-19B Section IV flow testing. Section IV experimental data will be compared to numerical predictions. We present successful predictions of pressure transients that match experimental data. The second component of the software evaluated and characterized in this paper is the pressure, volume, temperature (PVT) accuracy and its implementation. NIST thermodynamic data, together with shock tube examples with pressure and temperature ranges relevant for deep-water completions will be used. We demonstrate that, although the current PVT implementation is accurate on typical downhole jobs, it could have limitations at higher pressures and temperatures. Finally, we present an improved numerical implementation for the modeling software.

This paper describes the operational planning and process safety due diligence performed to ensure safe and successful operations in the world's first deepwater propellant perforation in a carbonate reservoir. The Malampaya gas field in the Philippines is a depleted carbonate reservoir with five subsea development wells. The Malampaya Phase 2 Project that concluded in Q2 2013 involved drilling two new infill wells MA-11 and MA-12. Given the uncertainty in prognosis (Carbonate K-Phi) and the greater risk of not securing wells with high deliverability as per the well objectives, it was decided to use some form of near wellbore stimulation to bypass the near well bore damage zone caused by cement losses and cuttings lost to the formation while drilling the 300 m reservoir section. Propellant perforation technology solution was selected based on optimization of rig time, ineffectiveness of acid jobs in a karstified, fractured carbonate and process safety considerations of acid handling on a dynamically positioned rig. 200 m reservoir section was perforated safely and successfully with 3–3/8″ propellant perforation gun with 30% propellant loading on a 2″ coiled tubing in each of these two subsea wells. A standard 6 SPF shot density and 60 degree phasing was adopted with deep penetrating charges to bypass the damage zone suspected from drilling and cementing losses in this depleted carbonate. Both the wells delivered finally in excess of 100 MMscf/day during the well test on the rig as expected. This paper outlines the expected vs. actual well performance; process safety due diligence with an elaborate modeling focus on the worst case scenario (i.e. no cement behind the 7″ liner). Static and dynamic coil modeling results are shared along with an overview of the transient modeling conducted to optimize the final perforation interval on both the wells based on the actual lithology information.

Perforation design including gun size, type, charge weight, configuration (shot density, entrance hole, phasing) and deployment options can significantly impact well productivity post perforation. Gun selection is a key process to ensure that the optimum gun that can yield maximum well productivity and minimum skin due to perforation has been considered. Gun performance modelling and sensitivity analysis should be conducted to compare the performance of various guns and to select the optimum gun suitable for well and reservoir conditions. Gun performance under downhole condition is a complex process and uncertainty analysis should be considered when converting API gun test data into downhole condition. It is always preferred to use stressed-core test data such as API section II/IV. However, data analysis and alteration might still be required to replicate the exact downhole condition. This paper presents a successful case history of perforating 130 m in a single coiled tubing conveyed run using Live Well Deployment system in 6,000-m deep gas and condensate reservoir with an average permeability of 10 mD and reservoir pressure of 12,500 psi. Production has increased by 20% compared to reference wells due to the intensive perforation testing and design process conducted to this well prior to operation. Extensive modelling work has been conducted to evaluate the performance of deep penetrating guns compared to conventional guns, in addition to uncertainty analysis and risk assessment regarding the impact of using API section-I compared to Section-II/IV data. The paper demonstrates a robust workflow for gun selection and gun performance evaluation process, which can be used as guideline to perforation design process.