Carlos Erik Baumann

A Combination of Perforating Technologies to Maximize Well Productivity and Minimize Rig Time

In this paper we describe the challenges and the techniques used to deliver zero perforation skin wells in the Blacktip gas field offshore Australia. We describe the software models used to evaluate both the well perforation design and the operational risks, and the approach used to reduce rig time. Software modelling based on historical experimental data and newly developed rock perforating models, showed that cleanup with dynamic underbalance would deliver the highest well productivity. Minimum rig time utilization was achieved with wireline conveyed guns.

Prediction and Reduction of Perforating Gunshock Loads

Most wells and particularly high-pressure wells are susceptible to gunshock damage when they are perforated with inappropriate gun systems and/or under suboptimal conditions. This paper presents a simulation methodology to predict gunshock loads for tubing-conveyed and wireline-conveyed perforating jobs. When planning perforating jobs in high-pressure wells, engineers strive to minimize the risk of equipment damage due to gunshock loads. The methodology described here helps engineers to identify perforating jobs with significant risk of gunshock related damaged, such as bent tubing and unset or otherwise damaged packers. When predicted gunshock loads are larger than the admissible loads, changes to the perforating equipment or job execution parameters are sought to reduce gunshock loads. This methodology enables completion engineers to evaluate the sensitivity of gunshock loads to changes in gun type, charge type, shot density and distribution, tubing size and length, number of shock absorbers, rathole length, and placement/setting of packers, among others. Fast gauge pressure data from perforating jobs shows that when model specifications are representative of the actual perforating jobs, the predicted wellbore pressure transients are accurate both in magnitude and time. Peak sustained pressure amplitudes at the gauges are on average within 10% of simulated values. With the methodology presented in this paper, engineers can evaluate perforating job designs in a short time, and they can optimize perforating jobs by reducing gunshock loads and equipment costs. The ability to predict and reduce gunshock loads and its associated damage is very important because of the high cost associated with most wells, particularly high-pressure wells. With the software presented in this paper engineers can optimize well perforating designs by minimizing the risk of gunshock related damage and the associated rig time losses.

Perforating High-Pressure Deepwater Wells in the Gulf of Mexico

A large number of well perforation jobs are conducted successfully worldwide each year. However, gunshock related damage poses a significant risk when perforating high-pressure wells. This paper presents gunshock studies done with a simulation tool specifically developed to predict perforating gunshock loads and the associated structural loads on the equipment. This simulation effort includes results from seventeen Tubing Conveyed Perforating (TCP) jobs on high-pressure deepwater wells, with pressures ranging from 13,800 psi to the highest pressure wells ever perforated in the Gulf of Mexico at 20,700 psi. The results show very good agreement between software predictions and actual field data. When planning perforating operations in high-pressure wells, engineers strive to minimize the risk of equipment damage from perforating gunshock loads, such as bent tubing and damage to packers. The risk of equipment damage from perforating gunshock loads increases very rapidly as the bottomhole pressure increases beyond 15,000 psi. The simulation tool used to perform gunshock studies is fast and can reliably identify perforating jobs that have a high possibility of gunshock related damage. For those cases where the chance of gunshock damage is high, design changes can be implemented to reduce or eliminate those potential risks. In this review, computational predictions are compared with high-speed pressure gauge data, with the residual deformation of shock absorbers, and with high speed acceleration data. Fast gauge pressure data shows that predicted wellbore pressure transients are sufficiently accurate in magnitude and time. Peak pressure amplitudes measured at the gauges are, on average, within 8 percent of the predicted values. Residual deformations of shock absorbers correlate favorably with predicted peak axial loads, and available fast gauge acceleration data shows that the asymptotic gunstring acceleration is well predicted, both in amplitude and frequency. The ability to identify and reduce risks in perforating operations is important because the value of deepwater wells is very high and rig time losses are costly. With the software tool presented in this paper, engineers can optimize high-pressure well perforation designs in order to minimize the likelihood of gunshock related damage and the associated rig time losses.

Perforating on Wireline – Weak-Point Load Prediction

Thousands of wireline conveyed perforating jobs are executed every month around the world; however certain jobs have a higher risk of weak-point breakage due to dynamic pressure loads, known as gunshock loads. Gunshock loads result from pressure waves in fluids and stress waves in structural components. Perforating under all conditions (i.e. static/dynamic overbalance or underbalance) can produce pressure waves and/or reservoir surge of large magnitude leading to wireline weak-point (WWP) failures and/or cable damage. These risks are assessed as part of the job preparations. In this paper we focused on Dynamic Underbalance (DUB) because perforating with DUB can deliver clean perforations with very low risk of gunshock damage when properly planned. For any perforating job on wireline, the magnitude and duration of pressure and stress waves depend on job parameters that can be adjusted, such as type and size of guns, shaped charges, gun loading layout, wellbore fluid, placement of packers and plugs, and cable size. For perforation damage removal we need a job design to generate a DUB of enough magnitude, using the right gun types and loading to produce a DUB of large-amplitude but short-duration, thus removing perforating rock damage while minimizing gunshock loads on the WWP. Perforating job designs are evaluated with software that predicts the transient fluid pressure waves in the wellbore and the associated structural loads on the cable and tools. All aspects of well perforating are modeled including gun filling, wellbore pressure waves, wellbore and reservoir fluid flow, and the dynamics of all relevant solid components like cable, shock absorbers, tools, and guns. When planning perforation jobs that may have a significant risk of weak-point breakage, we predict the peak dynamic loads on the cable and weak-point during the design process, and when necessary we make design modifications to reduce the peak load on the WWP. The software’s predictive capabilities are demonstrated by comparing downhole fast gauge pressure data (110,000 data points per sec), shock absorber deformation, and cable tension logs with the corresponding simulated values. Fast gauge pressure data from perforation jobs shows that the software predictions are sufficiently accurate to evaluate the gunstring dynamics and the associated peak tension load on the WWP as part of the job planning process. Residual deformation of shock absorbers correlate well with predicated peak axial loads at the WWP, and available cable tension logs from vertical wells show that the cable surface tension is well predicted. The simulation software described in this paper is used to minimize the risk of unexpected release of tools and guns due to perforating dynamic loads, thereby minimizing the probability of non-productive time (NPT) and fishing operations.